I like the telescoping ladder too. I ordered a ladder when I bought my trailer and now regret it. Most of the time I use the ladder is to inspect the slide, and with the mounted ladder I have to climb on to the roof to see the slide. Also, the ladder adds penetrations through the rubber and siding.
I bought a telescoping ladder on Amazon and it works great. I can lean it against the wall and climb up a couple steps and see/clear my slideout roof. No additional maintenance items either. And... it was cheaper!