You can also try some simple hand exercises to limber up your fingers.

To keep your wrists and hands nice and limber try this exercise:

put your hands together in front of your chest like you're going to say a prayer. Now lift your elbows until they're parallel to the ground. Slowly rotate your fingers towards your chest as far as you can go. Then rotate them so you point away from your body.

Do this for a minute or two each day. This will keep your wrists and hands nicely stretched, which will help you build your guitar playing stamina.

Peace~

Dave