It depends on your ROI mostly. If you have a low ROI you will need more BIs in comparison to someone with a higher ROI.
Take a look at this tournament variance calculator...
https://www.primedope.com/tournament...ce-calculator/
Play around with it depending on the format you play.
For example...Let´s say you play 6-Max tables where top 2 gets paid. And let´s say you play 2,000 games a month.
A player with a 10% ROI in those games will have a probability of loosing around 1% and the worst peak would be at -$84 (84 BIs). All this with a 99.7% confidence interval.
With a 95%, your worst peak would be at $23 so I'm guessing 50 BIs would be enough for that player.
But, on the contrary, a player with a 5% ROI under those same assumptions will have the worst peak at -$166 at 99.7% confidence interval and -$74 at 95% with a 12% probability of losing.
Playing those games with 50 BIs would be very risky to say the least.