Surfing Waves

I am an early intermediate surfer, and have been surfing a 9'0" longboard the majority of the time. I am in my late 30s and have entertained the idea of going shorter with my boards. So, I do occasionally surf a 7'0" and a 5'5" though my wave counts with those boards are way lower and my surfing is pathetic on those boards.

I envision with my old age, I will inevitably have to be a long boarder, Is it best that I just stick to longboarding exclusively so that I can become really proficient with that? Or is there any utility by persevering with the shorter boards, even if it means I will struggle and waste the valuable little surf time I get in my normal life? (will surfing other styles and types of boards ultimately make me a better surfer?)

thanks

I have a board I call the 'memento mori' board - I'm 46 and its a 'shorter' board (6'10 though so not that short) which I bought because I figured I was getting old enough that if I didnt try it now, I probably wouldnt be able to try it in the future. I miss a few more waves but its not a waste of time - could go shorter and maybe will (but I have no interest in going very short).

In any case

- 30s is not old, stop kidding yourself. You have a lot more aches and pains to get used to

- absolutely you can go shorter. Just be (a) careful in your selection and (b) dont do it too early. No point going 9ft to 7ft if you cant surf the 9ft reasonably well (at the very least, catching waves and bottom turn and going down the line and some kind of top turn, even if its not a cutback).

- if you dont try you will never know

There are plenty of highish volume boards around 6'8 to 7' you can aim for as your end point (or even shorter) - I suggest a transition board (mid 7ft) first, ride that for a year or two (depending on frequency of your surfing) then go shorter (so 9ft -> 7'6ish give or take -> 6'10 -> 6'6ish if you want).

Of course, there is no need to go shorter. But if you want to then for sure try it

Fitness is the key to learning to surf any sized board but if you aren't very fit and don't plan on getting fit them stay with longer boards or you will waste a lot of time not catching waves. Also the less often you surf the bigger the board you should use since your skills with deteriorate with lack of time in the water surfing

If you're a mountain biker and every time you go out it's on a different bike, that would hamper your learning. Different saddle height, suspension set-up ( preload, compression, rebound ), gearing, wheel size, etc. Best to get the basics down on one bike first.
That said, I feel a longboarder borrowing a short(er) board will help with timing the wave. A Shortboarder that borrows a longboard will learn glide and develope more leg strength.

All of the advice mentioned so far is pretty reasonable. I would stick with one board until you feel pretty comfortable on it, then drop in size to something mid-range (like mid 7' or so). Switching up boards can improve your surfing, but as waikikikichan mentioned if you do it too early or too often, it'll only slow you down. Get comfortable on one board so that when you do switch to something else, you can actually notice the difference and be able to adjust your surfing accordingly. Even after having been surfing for 20 years, switching to a new board that you've never ridden before can take time to adjust. If your time is limited, you want to focus it on improving your surfing, not adjusting to different boards.

I was surprised you mentioned that you surf a 5'5", that seems wayy too small. You're also not too old at all. I've got a friend in the mid 50s who just recently learned how to surf and gradually worked his way down to a 5'10". It's possible and totally manageable if you take the right approach. Keep it up!