It's 11Ah, so, assuming the bulb is a KPR113 (a reasonable assumption), you are looking at 11/0.75 or about 14 hours, if used continuously.
My experience with these batteries is they last up to six years with the kind of usage pattern you describe.
If you used it every day, I would +1 the SLA suggestion, and certain usage patterns could also suggest the 509 or 529.
But the 1209 is definitely the one I would choose.
But much will depend on what is on special while you are shopping. Any lantern battery made by Eveready or Duracell will be OK, even cheap Chinese ones are OK - if they feel heavy when you pick them up. They must have F cells inside them, not D, so look for a code "4LR25" on them if you are unsure.
If you see "4LR20", they contain D cells and will have only half the capacity, runtime and even shelf life!