> 3 days (over a weekend) is reasonable for a free tier, I would think. For a paid tier, maybe it should be more immediate.
For most services, I'd expect free tiers to be strict subsets of paid tiers. I'd expect them to be running the same code, often on the same servers, as paid tiers. Free tier accounts would for the most part just have different per account settings.
If that is the case, and I was a paid tier user, I would be upset if it takes days to respond to problems on the free tier because if free tier accounts are running into problems there is a good chance paid tier accounts are also running into problems.
Maybe the problem really is one that only affects free tiers--something like, say, a load balancer mistakenly thinking the servers are overloaded and dropping free tier requests to ensure that paid tiers get served.
Perhaps then maybe you can make a case that it is OK to not fix it over a weekend. But even in that case there should be a prompt investigation when the free tier users start reporting problems in order to determine if it is something that will also hurt paid tier users.
If that investigation finds that it won't affect paid tiers, there should then at least be a status update explaining this. Free tier users are going to be Tweeting about, posting to HN and Reddit, etc., where paid tier users are going to see it.
You need to assure your paid tier users that things are fine for them and they aren't going to have their weekend messed up dealing with your outage.