When the expansions are done with, assuming the game is a success, I think a 1789-1989 (or 1792-1991?) span would be reasonable. 1821 or 1836 as the initial start date, with a few more (1789, 1861, 1913, 1945) coming later. 100 years just isn't a lot of time, especially when compared to EU4's 400 or CK2's 550 (Hearts of Iron is a wargame, not a nation-building one), and while secondary bookmarks would take more effort in Victoria than in EU or CK, they'd also be likely to attract more interest due to covering a better-known period.
I suspect the economy system would be substantially changed in V3, enough to avoid the late-game issues in V2. Getting demographic information would be an issue, but past a certain point you can make details up for the sake of game balance. And I feel that 1790-1990 or so is a convenient span neatly delineated both by ideology (from birth to shattering) and by industry (from the First Industrial Revolution to the Information one).