You Dirty, Dirty Girl.

30 bands. 2 days. 1 pair of undies.

Where do I start?
There's so much wrong with this ad, I'm nearly soiling myself. And trust me - panty-liners won't do. For those who haven't seen it, the above is the byline for a recent advertisement for panty-liners, which shows a girl at a music festival who doesn't need to change her undies because of the wonder of feminine hygiene products.

First of all, if you have room in your rucksack for a couple of panty-liners, you've got room for a clean pair of daks. In fact, if you're anything like me, the daks go in first. The priority list for packing a festival rucksack, loosely, is:

1. Undies
2. Ticket
3. Money
4. Condoms
5. Phone
6. Gum
7. Clothes
8. .....
...........
....217. Panty-liners.

Secondly, and I'll put this as nicely as possible - panty-liners are for uncategorisable stuff. The stuff at the end of a few days during which a panty-liner ain't quite enough. The stuff in-between times for which there is no satisfactory word. And you know what's much, much worse than that stuff? Crotch-sweat and pooh.
The reason most girls don't bother with panty-liners is that uncategorisable stuff doesn't really bother them. The reason all girls change their undies at least daily is because of an innate aversion to crotch-sweat and pooh, and the unwillingness to be responsible for the collection of either. You can be sure that the paperless porta-loos and guitar-based entertainment of music festivals do their darnedest to encourage deposits of both.
No panty-liner, not even a magic panty-liner constructed solely from heaven's own sphagnum crop, is going to absorb all the evil things that undie-changing was invented to avoid.

Two days and one change of underwear?
Bags not sharing your tent, you filthy mole.