Multiple Sites - What do do with them.

I started a retail website a couple of years ago. I experimented a bit with a few different sites to get it going, using paypal on one and a different cart on another to see which I liked best. Now I have one site that generates 95-98% of the business and has #1 rankings on search engines, the other two don't do much. The main site is enough updating work to keep me occupied so I really don't want the other two anymore other than the fact that they may help with ranking.

What is the best way to get rid of them without hurting my main site?

If I point the domains to my main site will that hurt?

I've heard that have the main page redirect to the main site is not a good idea, and I've also hear pointing the domains isn't great either. Should I just remove those sites entirely?

or 301 redirect them, until they are eventually dissapear from the serps.

With a little work those other two sites might start bringing in some dough. I would not want to put all of my eggs in one basket - what would happen to you if your main site disappeared from google? This does happen to some people. So, my approach would be to put some time into the secondary sites.

It is nice to have several web sites indexed, use them correctly and you will boost your main web site's rankings.

if you dont want them anymore, sure get rid of them and 301 them to your main site as i mentioned , but like egol and sorvoja said, it is actually better to have many sites listed and there are various ways you can structure them to benefit your business.
wait until Sorvoja's 1000th post, im sure you'll find out what to do with them after reading that..

I find your subject line rather humorous...

"What do do with them"

do do ..... I feel five right now. haha

guess I should check my spelling and slow down with the typing.

I have thought of keeping them, its just the constant updating that makes me wonder if my time is better spent just focusing on one site. I'll hve to mull this over a bit more.

I Agree with EGOL, it is always good to have backup plan / Site.