Hi Isabellam,
I don't have a hard and fast rule on how many bags I have but I like to keep my numbers fairly small--like 10 or so total with a few extra tucked away for certain occasions. I've gone through another eBay sellathon of about 8 bags and am much much happier where I am now.
I would LOVE to be one of those people who has three bags and is totally content, but I find that I need a few extra to keep things interesting but not so many that I lose track. Almost all neutral colors with the exception of a couple and they have to be comfortable. If I haven't reached for it in half a year, I sell it. My criteria is, "Would I want to carry this bag tomorrow?" and if I have an excuse "too heavy, uncomfortable, etc," it ends up getting sold.
I've also gravitated towards smaller bags and messengers now that my kids are older and I use my Longchamp totes for all the other stuff I need to carry (scarves, water bottles, journals, etc).
I have my bags out where I can easily see them. I don't like clutter or tons of stuff squirreled away where I forget. I have a decent sized walk in closet but I like white space and room to breathe, so that helps. I would always feel stress when I had too many bags. It made me anxious for some reason.
I also found that if I had fewer bags, I really appreciated and enjoyed them more. When I was buying bags due to sales, etc., it didn't feel special. My goal for next year is 2 total, including one for my birthday at the end of the year. I think I appreciate things more when I have just a few styles that I really love.
Hope that helps!