In primary

How long can I leave the beer on the yeast before ill effects will set in.

BV

My own rule of thumb is no longer than four weeks.

Depends on strain, temp, gravity, nutrients, and oxygen. Most beers are ready to be transferred/packaged by a month. Any more time than that you, could be, playing with fire.

How long has it be at fg? Or how old is it.

It depends on several factors but I recommend no longer than 4 weeks

Years by my experience.

Thanks everyone. I was looking for a very general answer.  Four weeks seems to be right. On a slightly different track. I have always added fruit (figs) in secondary.  What are your thoughts on adding fruit to primary at the beginning of fermentation.

I add fruit to the primary after four days.  I’ve used strawberry and watermelon, never figs

I keg almost everything I brew after three weeks. If it needs lagering, I do it in the keg. Secondary for fruit and dry hop additions only.

Depending on the beer, you can easily go 2-3 times that long.