> Which increases the limit to 90 days

It increases to 365 days, no? At least thats the longest I can sign my app and I use a personal but paid Apple Developer Account

Oops yes you're correct. Edited post and put a note about the correction and a link to my previous post describing the correct details.

But it's only 365 days if you install the app on day 1 of your $99 subscription period.