Note that diamond (usually called PDC) drill bits have been in common use in the oilfield industry for decades now. Search PDC on your favorite search engine, and you'll find dozens of manufacturers actively selling them, each with a big selection.
Exactly how long you can drill with one varies widely based on a bunch of factors. You do have to pull the whole drill string to change one. It's slow, but not that slow. Most actual oil wells drilled have in the neighborhood of 10 or so trips in and out with drilling tools for the whole operation for various reasons. Varies widely of course depending on a bunch of factors, but that's usually the ballpark. Plus a few more for casing and cementing runs.
Exactly how long you can drill with one varies widely based on a bunch of factors. You do have to pull the whole drill string to change one. It's slow, but not that slow. Most actual oil wells drilled have in the neighborhood of 10 or so trips in and out with drilling tools for the whole operation for various reasons. Varies widely of course depending on a bunch of factors, but that's usually the ballpark. Plus a few more for casing and cementing runs.