As long as a bike is serviced regularly and kept clean it should last a good long time. It's always a good idea to have an Allen set and a bottle of lubricant on hand. I'm told it's also a good idea to wash the bicycle regularly. I've ridden my 21 speed Trek 4900 (which was the "entry level hardtail mountain bike) for about 15 years on mostly all the original components (barring a switch to hybrid tire and admittedly its overdue for a major overhaul.)Danl8 wrote:Good choice. Many gears can be annoying from a maintenance perspective...more to break or keep in order. However for climbing, you will be able to keep a consistent effort without having to overexert. I ride a 12-speed fuji which for Chester County PA is good enough. Shifting will take a little getting used to, esp. with 21 gears, but you will appreciate most of those when climbing. :-)
BTW, technique also comes into play. I recommend toe cages or clips to keep your feet in contact with the pedals and allow you to exert continuous effort throughout the entire revolution of the pedal. You want both of your legs to share the load equally to minimize fatigue - and as a side benefit to forestall chafing and inflammation to your undercarriage. That being said, I'd get several pairs of padded biking shorts and gloves with gelled padding.
I'd also recommend getting either a Camelback or a couple of water bottle cages and good squeeze bottles. I learned my lesson the hard way by riding over 30 miles on a hot summer day with only a couple of stops for water along the way.