I have a 75w ExoTerra Heat Glo heat lamp in a large Exo Terra Glow Light mount. This unit sits on the mesh top of my Stimmie's (an Anteresia similar to a Children;s python) enclosure. I leave it on 24x7 and the probe-measured temperature on the basking shelf 20cm below the top of the enclosure varies between 30 and 35 degrees at this time of year. I started with a 50w heat lamp but, because I was only getting maximums of 32 degrees on the basking shelf, I upgraded to 75w. I expect to use the 50w lamp again in summer when the ambient temperature is higher.
Hope this helps.