Or much much longer. It's not going anywhere. It can't escape its cask, and outside human intervention the casks won't be breached. It's just locked-up metal that gives off some radiation, fully contained within the cask. It isn't oozing green goo.
All the waste a plant ever produces in its lifetime can be contained with ease on site. Waste certainly isn't the main issue, though it's portrayed to be. Cost of deployment and staffing are more prohibitive issues, and both are surmountable. I don't think it's a bandaid for all power issues, but it's a powerful tool that should be used more often, not phased out.