When taking a look at the science system, it would seem that the incremental ratios eventually make specialist science improvement prohibitive. The increases trend as follows. First, the cost of the manuscripts increase up to about 240% of the initial cost in increments of 10 books, to a maximum increase of 90 books (10 levels). Second, the cost of Tomes increases about 208%-242% for resources and up to 500% of the manuscripts, in increments of 20 books (5 levels). Third, the cost of Codices increase 200%-224% for resources and up to 300% for tomes, in increments of 30 books (3 levels).
To see the effect of the increases, we can compare the cost of fully educating the first explorer to the fullest and the cost of educating one once the system reaches the caps. The explorer uses 5 manuscripts, 10 tomes, and 6 codices to fully educate. The first tier is filled at lowest level, costing 100 gold, 2000 nibs, and 2500 simple paper. For the tomes, the ratio will change half way through, costing 50/1000/1250 for the first 5 books and costing 55/1125/1375 for the second 5 books for the manuscripts to use, then 2500 intermediate paper and 2000 letters. The 6 codices will also be on split tiers for manuscripts, with the first 5 manuscripts costing 55/1125/1375 again and the final one costing 12/240/305 tier 1 resources. The cost to convert to manuscripts remains at the first tier, bringing it to 16 total, costing 1200/1500 tier 2 resources. The conversion to the codex will cost a total of 1500 advanced paper and 1200 book fittings. Total cost for investing all 21 books is 272 gold, 5490 nibs, 6805 simple paper, 3200 letter, 4000 intermediate paper, 1200 fittings, and 1500 advanced paper. There are a total of 21 manuscripts made, 16 tomes, and 6 codices made, counting those used directly and those used to make more advanced books. For a level 1 bookbinder, this will normally take (ignoring the reality of delays in starting new books) 1260 hours for the manuscripts, 1152 hours for the tomes, and 504 hours for the codices, for a total of 2916 hours, or 121.5 days. For level 5 bookbinder, this improves to 252 hours, 228 hours, and 99 hours respectively, for a total of 578.75 hours, or just over 24 days.
Now, let’s compare the same explorer that is educated later on, once all of the books have reached the final tier for cost. While it would appear to take some time, it is less than is immediately evident, as the element of consuming lower level books to make higher ones quickly escalates the lower books. By the time tomes have reached the 4th tier, the manuscripts would have maxed out even assuming no manuscripts were used other than in the production of higher level books. The same is true of the codex, as both lower levels will reach their maximal tier just past midway through the second codex tier. It will take 5 manuscripts to make each tome, and 3 tomes to make each codex, requiring 15 manuscripts for each tome. This will require the creation of 6 codices, 28 tomes, and 145 manuscripts. Total resources are 3480 gold, 68150 nibs, 85550 simple paper, 11620 letter, 16940 intermediate paper, 2400 fittings, and 3360 advanced paper. For a level 5 bookbinder, it will ideally take 2237.6 hours, or 93.2 days. For level 4 bookbinders, it would be nearly 117 days, for level 3 bookbinders, nearly 156 days.
Of course, this is for the explorer that only uses 21 books, as opposed to the geologist that uses 31 books, with 11 possible codices. For the geologist at the top tiers, it requires 11 codices, 43 tomes, and 215 manuscripts. For the ideal level 5 bookbinder, this takes almost 3374 hours, or 141 days. As the trees for the generals have not been posted yet, it is not possible to give accurate times; however, if they have comparable trees, it would again range in the 93 to 141 day range. The bookbinder buffs will double to production speed for 24 or 36 hours, which means that in order to cut the time in half for the two specialists, you would only need 47 glues or 31 resins for the explorer, and 71 glues or 47 resins.
So, just a casual look at the skill trees and what it costs to make them. It would seem that in the short term, it is more productive not to invest many books into the specialists, and instead use them to make higher books first, as the initial higher books will cost less. Over the long term, this benefit will not be that great, and you would not be able to benefit from having the system for some time. The overall cost for each specialist can also be lowered by the fact that you can use lower level books than the highest accessible tier to open further tiers. However, this also has to be balanced by the loss of abilities that can be gained by higher book placement.
In summary, it would seem that the time required as you progress in the science system does allow it to expand at the same speed of otherwise normal play. At the highest levels, it takes over 3 months to fully invest an explorer and over 4 months to fully invest a geologist. And as there is no queue for book creation, this ideal time is likely significantly off to account for not being to start new books immediately. So, given some basis for discussion, perhaps we should discuss it and give appropriate feedback on how this can be improved.