Slow question

[sacr3d]

Hello,

I've been installing ROM's for awhile and love the customization people bring to the table. Problem is every time I install a new ROM its always fast (generally), but eventually becomes sluggish. I delete and purge off old text messages and it makes a small difference in speed and I do restart my phone often. Is there anything I'm missing here? or does this happen to others?

If not can you give me a few pointers on what I should be looking for.

Thanks!!