If he wins a no confidence vote, they can't challenge him again for a year. Meaning that come mid 2023, when the economy is even more destroyed and voters are even more on their knees, he has to take them into a general election unless he stands down. Which then leads to a further leadership contest, and they get messy, leaving his incumbent with less than a year to get things in order.
It's a mess for them either way really.
If starmer and Raynor get done for beergate and step down, Boris could potentially be coming up against Burnham, who is one of Labours most popular figures as well.