I don't know how long it will last, but I've been using a piece for a few months and think nothing looks nicer/more natural for a basking area. It floats and I had to cut it to wedge in between the sides of my tank. Don't know how you'd make stairs, but if you buy a curl--not a flat piece--so that part of it extends below the water, your turtle shouldn't have a problem getting on it. My turtle easily grips it to climb on. I bought mine at www.blackjungle.com
Before using it, I used a brush to gentle get off any loose pieces, and I let it soak for a few days in clean water to release some of the tannins, changing the water when it became discolored. I dried it in the oven for about 15 minutes to kill anything nasty on it. Some people don't soak/rinse it, and if you don't, your water may become discolored. It's not bad for the turt, just not that nice to look at, and it will lessen in time. HTH