Will shorter infusions for mental health still be as effective after a longer one for pain?

I have been doing infusions monthly for about eight years. I do well with them and they help keep me on steady ground mentally. I also have moderate to severe neurological pain. I’m considering paying for one or two long infusions for my pain. Theoretically - I believe - it’ll be the same dose just for a longer time. So there wouldn’t be any more in my system at any given moment. However my worry is that somehow if I do the ones that last for hours - if I return to the 50 minute ones- I will lose the effectiveness of the shorter ones for my mental health. Anyone have any advice or experience in this area? Thanks.