I am in alignment with everything you have said.
Unfortunately, I am at a bad time for online stuff until July (timewise due to offline busy season) ... Ideally, I should be concentrating on "breaking the server" with traffic and revenue records and then peel away the winners (or losers?) to ease the load. Unfortunately, without traffic and revenue records it's an added burden financially to just double up or wait for things that aren't happening quite as planned. I either have to move - or stay.
Originally Posted by Eric
The thing is, there's no easy way to estimate what you need until you need it. It's based on so many things (that I mentioned in my previous post) and I'm unfamiliar with any calculator where you could punch in the variables and see what resources are required.
Shared servers can be hit or miss. Sometimes the server you're own is great and always up. Sometimes there's a user on the server that always overloads the server. Sometimes hosts don't oversell the server too much... other times they do.
My experience with shared hosts, VPS and dedicated servers is that I eventually always out grow them. Usually this is because of traffic to my site. So I consider it a good problem. Because the more traffic, the more revenue I have. The more revenue I have the more I can spend on servers to keep the sites up more often.
But honestly I can't really answer your core question. It's a really difficult question that depends on so many unknowns.