Cacheing - a bad idea för certain sites

[Slackervaara]

I have a site with 10 000 articles and 500 000 forumpost plus other content. I decreased overload by excluding bad bots. But when Bing Bot started to increase bandwith 10 times problems returned. i started to suspect that cacheing might be useless as I have only 20 000 visits per month. I looked in Cpanel Awstats and found that only 25 % of pages were by visitors rest robots. So only 25 % of files in cache is visitors and the rest are robots induced files. So I disabled cache and used JCH Optimize instead and the load on the server decreased considerable. I guess resources are needed to create cache-files and then to find the right file from cache. Then the cache is flushed after 15 minutes. The cacheing would be better if bots could be excluded but I think only JotCache had that nice feature. Have anyone else experience with this?