the pumps normally last a long time, but they arent intended for heavy duty use... so for normal usage while living in the trailer, there should not be an issue...
the shurflo pumps are about the best your going to find.... you can find more expensive ones, and a lot of cheaper brands, but for dependability stick with shurflo.... I just replaced the original pump in mine with a shurflo 4048 model, which is a bit of an upgrade from the oem pump which was rated at 40psi and 2.5GPM.... the 4048 is rated at 55psi and 4gpm....
but remember when purchasing a pump, they are NOT rated at a specific GPM at a specific pressure.... the GPM stated on the label is a free running pump with no pressure being built... and the pressure rating is what the pump shuts off at...
with some of the better pumps, there is a cheat sheet included that gives the approximate GPM at an approximate pressure.... for example, the 4048 which is rated at 4gpm and 55psi, actually delivers about 2.5 gpm @ 40psi...