When I used to sell production printers, I would walk into accounts that had 10+ year old machines (from any of the major manufacturers like Xerox, Konica Minolta, Canon, etc) that were working just fine. Since the components within the printers are modular, it's very much like a car in that if you keep replacing parts, they will keep running. However, you should be aware that manufacturers are only required to support a model for 7 years beyond the last year that model was sold. This is called "End of Life". They can stop making parts and supplies at this point. Most of the time, manufacturers will go well beyond the 7 years, but your maintenance click charge will gradually increase as it gets older.
Another thing to be aware of is the monthly duty cycle is a non-realistic perfect world scenario. It's slightly different for each manufacturer, but it's generally based on running 8.5x11 (A4) 20# bond at 5-7% coverage. Since most shops run heavier weights on color machines, much heavier toner coverage, and 12x18 or 13x19, that number is drastically reduced.
But to answer your question more directly, yes, using it lightly will make components last longer. To give you a time frame is nearly impossible as every environment is different. Manufacturers love to flip your equipment every 5 years when the average lease ends, but the machine can often go several more years without much trouble if it was lightly used.
An office MFP is pretty much the same as described above, but only when used as an office copier. If you try to use it as a production printer, doing long runs, on heavy card stock for example, your going to wear it down really quick and your service provider might push you towards upgrading to a production unit or face increased fees when it's time to renew your service contract.
