I've planned 3 future seasons, all 4 meant to take over about a year (long time in bird's view).
As for when I finish, well, my first season was 62 eps~over 3 years of work, and maybe the next will be around 50 (may or may not include filler). and I'm a lot faster than I used to be, so I'm guessing I'll be done with the series in about 4 years, maybe 5 to give myself breaks and/or improvements.
Tidbit: More on "time", my timeline is a bit scuffed/random, not the canon time per se, but the seasons/weather. Didn't plan to make the series a long form, but originally a comedy only, until I got deeper into lore and story. Just wasn't thinking, so for this first season, pretend it's winter, and they have evergreen trees XD