Most of the time, my computers are shut off during the day and night if I'm not actively using them. I sometimes leaving them running for a day or two if I'm busy for the weekend.
Thats what I did with my first Mac Mini, the 2005 original. It packed a sad after about 4 years, in need of a new power supply (had to deal with a very poor mains supply where I am, with many outages and surges) and a failed HDD.
I decided it was more cost-effective to get a new Mac Mini in 2009, the base model with just 1 GB RAM. That has been on nearly 24/7, in sleep mode when I am not using it, and only turned off when I take it to work occasionally, there is a power outage, or I am going away for more than a few days. It did slow down considerably in 2012, and it started to get a bit hot with the fan cracking up enough to be audible. An additional 4 GB RAM (5 GB in total now) an update to Mountain Lion (which I am still using)……
and most importantly, a clean out, restored performance.
Late last year, 2015, it started to heat up again, and it got a bit dicky. Another clean out restored operation to normal, and it continues to run well, with the original 120 GB HDD (plus an external 500 GB for extra storage).
Coincidentally the mains supply was improved in 2009, I installed an earth (now on 3 pin plug) and I got a better UPS with auto voltage regulation (the old one was cooked in a surge that resulted in a blackout for half the south of Thailand), all of which has made for an easier time for the power supply.