you need the contact lens specific checkups to make sure that your eye physically is OK, not just whether the prescription is correct. One every year i think is the minimum my optician likes, but prefers every 6mo (it costs me nowt, I’m on an aftercare plan anyway)
I have bought from daysoft as well, but they require you to confirm you’ve had a check up in the last x years (1 or 2, I can’t remember) and also require the contact details for your optician. I doubt they ever check this up, but it’ll more be a self protection thing so if you have an issue because you haven’t had a check up recently you can’t claim you weren’t told you needed them.