How long is too long to leave beer on trub

Hey , guys, quick question for you. I have a Saison going in primary at the moment, using a yeast strain blended with brett, and I wanted to leave the beer in primary for an extended amount of time to let the Brett do its work and funkify things. But I also wanted to wash the yeast and harvest some cultures to re-use in other beers down the road.

How long is it safe to leave the beer on the trub before I wash it? If I leave it in primary for a month or longer, will I still be able to harvest a viable strain of yeast to re-use? I know that autoalysis is fairly uncommon in homebrew situations, but I just want to be safe and know that I am collecting viable saccharo samples. Also, since the yeast has Brett in it, I would really prefer not to move it into a secondary vessel...

Thanks for any help and input guys!!

I had yeast alive in a 4 months old cake from a triple. Used it to ferment a dark strong.
You should be ok even at 6 months IMHO.

I had an amber ale stay in primary for over 4 months and it turned out great.

The brett will feed on the sacc. You can leave the beer on this yeast for a year or more without issue.

Harvesting yeast ....... the sacc will probably still be present for at least 6 months. The Brett will still be working for up to 18 months.

I'd harvest the yeast, the Brett will still be viable, and would add some new sacc yeast for the next beer just in case.

Hmmm, thanks for that guys . I didn't really plan on letting it go for much more than a month, so I will wash as normal and brew another one to let it age for longer