Been surfing short board and longboard for over 30 yrs before I took up SUP surfing 8 years ago, never really stopped surfing but focussed more on SUP longboard and short boards, for me it just a continuation and extension, same as STC, I love to move around on the board regardless of SUP or prone, cross step and more pressure on the rails, all about the angles on take off are all part of the challenge.
If I had to do it all again I wouldn't change a thing, coming from a prone background helps you understand the line up dynamics...also makes co existing with surfers in general way more easier as you know what they are thinking. I also enjoy my own space, so SUP gives me this freedom not to mention the benefits one gets from the ocean, the ability to move around quickly, see the waves approach from way off, paddling over reef and sea life are all apart of the SUP experience you really appreciate this more when you've had years of "prone surfing", also being in my 60s I'm not really bothered with who or what anyone surfs on nowadays

stay stoked, stay safe