A mesh system fixes dead zones by spreading your signal across three different nodes. It should last you five to seven years. You are buying this so you do not have to think about your internet connection for a long time, so choose a system that covers your entire square footage.
Router brands usually refresh their lineup in the fall. This is when last year's tech gets its deepest discounts during holiday sales. If you use the Discover it® Cash Back (Discover), you can spread that cost out over more than a year while your signal stays strong.
This 15-month window is a deadline, not free money. If you still have a balance when the 15 months end, the standard interest rate kicks in on whatever is left, which makes your hardware more expensive than it needs to be.