Well, we all understand about knitting just one more row or 10 or 12. I'd say the timer is a good idea unless it makes you tense up and knit faster because of the time constraint. You could try knitting one block or half a block or some number of rows at each sitting.
Antares' idea is a good one. Take a small sample of the blanket, maybe 4 squares sewn together, to the shower to give an idea of what this lovely blanket will look like.