I go between finger style and plectrums but I always keep at the same length. I used to play down by my knees back when I was cool but these days it sits slightly lower than if I were sitting down. I'd have no issues changing mid set, you do what you have to do. Whatever works.
[quote name='iamapirate' post='719128' date='Jan 20 2010, 03:28 PM']I'm 6 ft 3 so I can't really get my strap much lower than waist height. Anyway, sitting down and playing I actually find uncomfortable sometimes, but I always practise standing anyway.[/quote]
You can. I'm 6'3" & you can buy extra long straps. However if you develop back problems in later life I've never heard of you!