Bed size?

Would knowing what you want to grow for the next 5 - 10 years dictate the sizings?

Feel free to shoot me down if it's a stupid question

Not really. I think 2 foot is a good width for any crop either in a single row ie brassicas, tatties or in double or treble rows for onions leeks etc.
I like to grow a bit of everything and can't see a problem. As i said, this is just me thinking about what I am going to do and exploring options.

The reason I asked this is because my main beds last year (1st year on the plot) were 3 x 1.5 metres, 3 of them. They did me proud but I found them a little large to manage easily.

Because I want to try and grow a lot of perennial veg I'm going to use them for this, my thinking is once planted I shouldn't have to work them as much as annual beds?

As mentioned in other threads my annual beds for this year are a number of 120x80cm pallet collars, easy to manage (me thinks), I've left a wheelbarrow width between them. Granted I've probably wasted as much area as I plan to use but for now I think it's more then enough for me, I'm sure time will tell.