The 90 day period was kind of a throw around time frame when that was seemingly the average time frame it took to recover, it's not a hard fast rule.
None, or at least, minimal masturbation will speed up the rebooting process for seemingly most people. Especially those with PIED, people who have not developed PIED and older men seem to be able to get away with masturbation and still make relatively quick recoveries. This is probably due to the fact that they grew up Ming without porn, unlike this generation, 95% of this generation M'd with porn which likely created a strong linkage in the brain between M and P which indirectly activates porn pathways to some degree.
It's not impossible, it is very hard but many people do it! The less I touch myself the easier it is to avoid M (bathroom use only), avoiding morning holds and sitting around watching TV without touching yourself helps. If you're not watching porn and doing your best to avoid masturbation most of the time recovery will come, it just could take longer, how much longer? Who knows.