Burnout and tunnel vision would certainly ensue in the medium term; or someone external would intervene and snatch the programmer from you, by proposing them a

Burnout and tunnel vision would certainly ensue in the medium term; or someone external would intervene and snatch the programmer from you, by proposing them a better deal. It can still serve you well, depending on the market you're in, and how steep / long is the learning curve of your codebase - but I would argue it's not the best strategy in the long run.