There are some things to consider in all of this.
- Why did the outage happen? (Is it just your server that was hosed or their entire datacenter? If it was a larger outage, like a whole datacenter or their entire WAN connection, then you should be less forgiving. If it was a single node, then maybe you can be less austere in your judgement.)
- What has been done to prefent it from happening again? (Hopefully something is being done differently.)
- Was there transparency with the host during this outage? (This is a big one. If you don't know the answer to the above questions, then immediately find a new host.)
- Does it violate agreed upon SLAs? (If there are no SLAs or they're suspiciously low [95% uptime] then leave immediately. Keep in mind that two days out of a year technically does not violate a reasonable SLA of 98% uptime even though two consecutive days is excruciating.)
- Do you even have an account type that has an SLA? (If it's just a low end shared host, you probably won't have an SLA and thus are getting what you paid for. VPSs should have better service, though.)
- What can you get out of it to make the trouble worth your while? (If the outage was specific to a single device, the host is taking steps to prevent it from happening in the future, they were transparent about the process and they have a decent SLA [98% or better] that was clearly violated then see what you are offered for the trouble. Perhaps it's worth staying if they're otherwise a good host and are continually improving... and you get a few months free.)
Also know that it's not enough to just tell a host that you've lost productivity. You need to be taking measured samples of data that is important to you so that you can bring your own data to the table. In many instances, you have to prove to a hosted provider that you've lost revenue to be able to capitalize on repayment promises. If you have no data of your own, you're at the mercy of the provider's data which has its own interests in mind. They won't just take your word for it that "I've lost money because of this!".