The Far Future Survival mode is challenging to complete, but it can be done. Because of the massive amount of jetpack zombies, bug-bots, and disco jetpack zombies, Blover or Hurrikale are musts unless there aren't any jetpack zombies or Disco-Trons. This is true, although combining a Spring Bean with plant food and a Blover are effective at defeating whole waves of zombies because of the massive amounts of zombies with machined health.
Alternatively, if you don't want to use Spring/Blover, E.M.Peaches effectively stop machine zombies in their tracks. It is advised to use E.M.Peaches sparingly unless it is to stun a machine zombie that is too close for comfort, so that you can keep them for when the next wave rolls in, bringing out a large group of machine zombies.
Power Tiles are on the lawn too, so try to use them to maximize you plant food's effectiveness by planting sun-producing plants and the plants that deal a lot of damage on them. Keep these in mind, and you should make it through without a hitch!