this is just a mathematical reality of LEO satellites like this. They are hitting the thermosphere which causes drag and they need to constantly adjust their altitude to keep in place and not fall to the earth. Currently 5 years is all the fuel they can carry. If they were higher they would last longer but the network latency would be very bad so it's a tradeoff.
whether or not we need this LEO constellation idk but this isn't some big gotcha. Elon (and everybody else) would love to have longer LEO orbits but until there is some new tech this is what we've got.