Depends - for us it's a none issue. We don't have vendor cover on any of our servers (HP DL360 G5 and G7s, DL380 G6 and a couple of DL380p G8), what we do have is server redundancy (i.e. every server has a "warm" duplicate that could be swapped to with a few minutes of effort), and spares of older kit is cheap and plentiful (e.g. via I.T. recycling/brokerage companies or even ebay) enough that we have a couple of complete servers on a shelf as "cold" spares, in addition to common spares such as hard drives, PSUs, fans, RAM etc.
When I took over I.T. for our site, it was more important to me to standardise our servers (e.g. before we had a mix of Dell, HP, self built etc), and have "lots" of inexpensive servers rather than refreshing a couple of really high spec new servers (and having all your eggs in one basket type position) every 3 years or so.