London - Paris every month, cheapest way to do this regularly?

I’ll be coming to Paris regularly, 3–4 days at a time, roughly monthly. Trying to find the cheapest way to do it.

I keep hearing about Eurostar Snap. Can anyone explain how it actually works and whether it’s worth it for someone travelling this often? Does booking normal fares early beat it? Any tips for keeping costs down?

Also, is flying a bad idea, or does it work out cheaper once you factor in transfers and time?