Hey Serpenteyes...
I think you understand this, but it's something that might not be so clear from my wording. I am not a writer at heart (I'm more of a rules lawyer and munchkin I guess...), and it could be possible that you think to advance to the year 1550 you need to set aside an ungodly amount of PL all at once... which is not at all what I intend. These two tables below should better explain what I mean...
To go from 1500-1510 in turn 1 you set aside 55 PL
To go from 1510-1520 in turn 2 you set aside 55 PL
To go from 1520-1530 in turn 3 you set aside 55 PL
To go from 1530-1540 in turn 4 you set aside 55 PL
To go from 1540-1550 in turn 5 you set aside 55 PL
To go from 1500-1520 in turn 1 you set aside 210 PL
To go from 1520-1540 in turn 2 you set aside 210 PL
To go from 1540-1560 in turn 3 you set aside 210 PL
To go from 1560-1580 in turn 4 you set aside 210 PL
To go from 1580-1600 in turn 5 you set aside 210 PL
Each turn costs seperately as you can tell. Every turn you set aside X PL to get Y years, and that gets added to your lot. Next turn counts seperately. So in order to reach 2000 you could spend 55 PL every turn for 500 turns, 210 PL every turn for about 250 turns I guess, or 1275 PL over 10 turns, or 125250 PL all at once. The most logical route, In My Opinion, is to get PL up to about 1275 ASAP and have some strong allies to defend you, then research for all of 10 turns...
BTW, I'm going to have some quick and simple trade rules for players that want to profit from trading with each other. Things like a +10% to advancing civilization, and GP gained through yoru IR... something like that, but it will just be a simple rule.