Depends on may things: feeding schedule, sufficient hiding places for your dithers/cleanup fish, piranha temperament/character, tank space (yours is definitely a bit cramped), and more.
But all tank mates are potential meals, and may dissapear all of a sudden, even though they may have lasted many months or even years.
In my case, the longest-living tank mates are:
11 months: my 2 pleco's
9 months: 2 fivebanded barbs
8 months: 5 bronze cories
And some more that are in there for more than 5 months already....
Well strike out the Bala Shark. The P's took it out this morning. Total time = 21 days. I kinda cheated though, I haven't fed them feeders for a week... just flakes. I also sold the Pacu so i'm down to the reed fish and the P's.