You might want to consider going to the pintleless type that were made available by Nissan in 93+ Zcars. They are less prone to failure and are better injectors that the old style. . Look into what parts are required before going this route. There are also after market injectors and upgrades.
Have you been using Ethanol fuel? Biggest problem with this fuel is corrosion especially if not run often as you describe. Terrible stuff for engines. It needs to be eliminated from use, not really saving energy and improveing the environment. A typical government subsidy program to create a market.
