do you build you sites all the same layout or change them about

at the moment i have been using 2 or 3 of the same styles of building my websites but i think i might make more sales if i add some differing layouts to what i am using at the moment do you think it is a good idea to change around my site layouts every month or two so that they all do not look the same?

i dont just want to change the colors on my sites though but actually where ads and pics show up as well as the sizes of the pics and ads and how many pages each site have on them would this help me make more sales you think

variety is the spice of life, my friend! Different designs make a huge difference.

It would depend on the site. If it acted like a hub where you relied and repeat visits from surfers, then changing it too much might drive repeat "customers" away, especially if the changes affect the way they navigate the site. If it is just individual free sites and galleries, I say go for it. Experiment, do crazy stuff.