Has anyone considered replacing a big part of their lawn with creeping thyme? I'm thinking about it but can't find a lot of info on how to do it.

If you're walking on it, there are bees to consider when it's in bloom. Depending on how tidy you want it to look, you may need to trim the bloom stalks when it's done blooming. Some varieties need trimming more than others, I think. Even the lowest growing will mound up a bit, so that needs to be taken into consideration. I've seen pictures of a few combined varieties used as a "lawn", and they can be quite lovely in bloom. If it's a heavily walked on area, you'll need stepping stones. It can take some stepping on, but probably not constant traffic.

Dichondra makes a better lawn for walking on.

Thank you Sherry and Ann,
I didn't even think about the bees... that's a good point, as much as I love them it is a concern. They do look beautiful when in bloom but when they are not it may not be so attractive esp in Winter. Dichondra may not be suitable for where I am but I will look into that, thanks!

Do any of the creeping thymes stay evergreen in temperate winters?

I have not had great luck with any of the creeping thymes in the Pacific NW, and I've tried quite a few. The best one for me has been Red Creeping Thyme (Thymus praecox 'Coccineus') which stays evergreen if a bit sparse in the winter, then puts on fresh growth when the weather warms up. Most of the others tend to die out in the center.

An alternative you might consider is Smooth Rupturewort (Herniaria glabra) which does stay evergreen, spreads nicely, and seems to be hardier (for me) than thymes.

I have Elfin Thyme (Thymus serpyllum 'Elfin')

in one of my gardens, it will go great for a few years and than die out, noticed the same effect on a few other gardens.

I had the same experience with Elfin.

Does smooth rupturewort take foot traffic?

I have it in the expansion joints of my sidewalk and it has done well there. I don't worry about walking on it, but haven't tried it anywhere that gets real regular foot traffic, so can't really speak to that, although internet sources seem to agree that it can take light to moderate foot traffic.