I, too, go through periods when I do so little photography the chemicals would go bad. I solved that by using one shot solutions - particularly HC-110 as the film developer. I store the unmixed container in my refrigerator and mix what I need when I need it. I bought the bottle I'm working from now more than two years ago, and it still works fine. Kodak recommends mixing a stock solution - I never do that. I generally use dilution B, which means I use one ounce of developer with 32 ounces of water, or for small format 1/2 ounce with 16 ounces of water.

Rodinal will also work that way. Mix the developer 1:25, 1;50, 1:100, etc.

Another solution may be to mix your own chemistry - ABC Pyro, Pyrocat HD, etc. as one shot developers.

I have heard of people freezing developers, but I don't know how reliable that has been for them.