Why is the forced air heater not working?

No heat last year: changed igniter. Was chilly yesterday, turned heat up to 68 (had been on 66). Turned electric rm heater on last night @ 4 am. Got home today and was freezing. TO THE BASEMENT: Heater was humming, opened door, igniter was blazing red but no heat. Closed door and changed filter (which wasn't that bad) but no heat. Opened and closed door, checked connections but no heat and now igniter not coming on. Can change igniter but if its the igniter why was is on when I first opened it? Thinking igniter failed because had been running since the am hours nonstop. Or when I checked connections made it go out?(but I don't remember it being THAT delicate) Have to change igniter but won't if there's a deeper problem that will result in buying a new furnace. BTW, bought house 5 years ago & just had to replace the water heater- do they last around the same amount of time and therefore this needs replacing too? (I don't know if they were purchased at the same time but am uming)