Normally my sand paper lasts a day or so with palm sanding, is there something I can do to make it last longer?
Sandpaper is a consumable, and in fact people should be encouraged to discard it more readily as it's very common — and not just with amateur woodworkers :-) — to use paper until it's worn out and no longer cutting as it should. Using worn paper doesn't give uniform results and of course has a reduced cutting action, directly leading to many of the issues people experience when sanding as they try to compensate for the slower results e.g. by pressing harder, which is always something to be avoided.
We can't diagnose the situation in your case properly without more details than you've provided.
The type of wood you're working (harder woods v. softer woods, resinous v. non-resinous) and the type of sandpaper you're using have a pronounced impact on what you can expect of your abrasive. But perhaps most important of all is the area of wood you're working.
If you're working softwoods, these have resins in them that are well known for clogging paper so yours may not just be worn but also clogged (see related Question, What are these brown spots on my sandpaper?). One additional tip is to dust down regularly, to remove any excess sanding dust that may be on the surface. Even with a sander hooked up to dust extraction this can help.
If your paper is actually wearing out it may be because it's of lesser quality, where the abrasive particles are bonded to the paper backing with less resin/glue or with a weaker one (cheaper glues tend to let go when they warm up in use). Even when sanding by hand the difference between a quality paper and a cheap paper can be remarkable, you can easily sand for five times longer with a good paper compared to something cheap. A really excellent paper will outlast the low-end competition by a factor of ten or more.
Getting "a day or so" from your paper unfortunately doesn't tell us how much sanding you're actually doing. This could equate with working periodically throughout the day, sanding a bit then doing something else, but you might be production-sanding panels nearly continuously and obviously the wear on the paper would be completely different. In the first case a day would usually be less than you should realistically expect, but in the second case you'd be doing very well :-)
Regardless of what part of the above might apply to you I think you might want to look into Abranet, made by Mirka. This is not your granddad's sandpaper. New users seem to universally be instant converts and specifically rave about how long it lasts, here's Chris Schwarz waxing lyrical about it.
First and foremost don't buy cheap sand paper (Harbor fright), personally I like Norton 3x, but keep in mind sandpaper is a consumable product. If it's the cost of the sandpaper that you are concerned about, have you looked at getting a card scraper setup, yes it has a bit of a start up cost, but it's a one time cost and will greatly reduce the amount of sanding you are going to need to do.