Yes all the time and all the way up the neck. It makes finger positioning much more efficient, playing ‘Master Blaster’, for example, is much easier using the B string
To learn and stretch yourself? If there isn’t at least one musician in the band im in awe of i get bored quite quickly. Luckily, im mediocre so the bar is set fairly low!
http://www.ebay.co.uk/itm/322824933568?ul_noapp=true
Purports to be a Jaydee Celeste 5 string - it's not real though is it?
If it is then it looks like Jaydee simply couldn't be arsed with 5 strings and were trying to put people off.