Playing vanilla FtG or a mod?
It´s not impossible. If you don´t have level 6 by 1492 then you are doing something different. Perhaps your BB is high which raises your stability costs and you are always investing in stability instead of land? Or you have invested most of your research into infra / trade ( which is a sound strategy to later have a higher income) and neglected landtechnology? Or you lose taxes because enemies constantly pillage your provinces...?
Did you declare lots of wars and your stability is permanently not +3?
Or perhaps you are not emperor the whole time - being emperor gives a small bonus to income.
The expected years can be found in FortheGlory/DB/Technologies/land.txt
Land level 6 is:
Code:
technology = {
id = 6
average_years = 76 #1495
infantry_fire = 0
cavalry_fire = 0
artillery_fire = 0
infantry_shock = 100
cavalry_shock = 400
artillery_shock = 500
land_attrition = 1.00
land_morale = 2.00
sprite_level = 0
era = 0
}