Ok, I googled around on this and the reason why people "outgrow" the more affordable VPS offerings seems to be because of the size of the database. The size of the database grows as more and more posts get stored in the database. That's why some forums have old thread pruning policies. How many threads over a couple of years old do you think people actually look at and read again? I suspect its very small. Therefore archiving very old threads may be a plan. I don't think this site gets too much traffic to be problematic if the number of new posts per day is any indication. However I notice nginx is preferred over Apache and Postgres over Mysql for heavy traffic loaidng. Also gzip compression on page loading. Sometimes its better to do a bit of performance tuning before running off to sign up for an expensive hosting plan.