A heat press’s lifespan is typically evaluated by its number of “hits” or times that the upper platen lowers to the bottom platen. I would guesstimate that a user will get at least 100,000 hits out of any major-brand heat press. Some air models have been designed to last for more than 1 million hits.
A quality heat press built by a reputable manufacturer will last for years due to its well-designed components and mainframe. The only things that will need to be replaced based on wear and tear are parts like pads and switches.