The IR-90/91 is a very common Ink Roller used in Sharp Cash Registers, Samsung Cash Registers, SAM4s Cash Registers and Casio Cash Registers. They can last for awhile and of course it depends on your volume. They can be stored for awhile if you take care to keep them sealed and out of direct heat of course.
Never try and re-ink one of these, it will ruin the roller and more likely ruin your cash register printer. They don't cost that much so don't try to save six dollars and re-ink one. Throw the worn one away and replace it with a new factory inked one.