It's tempting to skip releases unless there is something that you desperately need from the latest release. Having said that, when I was contracting I used to upgrade every year usually on SP4.0 (when everyone else has done the bug testing).
Large assemblies / complex models don't always update as expected -- mates flipping geometry changing unexpectedly in complex models is the norm rather than the exception in my experience.
In a larger company, I'd set up a test machine and see what damage, if any, the upgrade does to your models. Then wait for SP4.0 or 5.0 and upgrade when everyone is on holiday.
Updating by using the "admin image" approach can save time by not requiring each seat to download the changes. It can also assist in keeping everyone on the same version.
2013 has a CAD Admin panel in the Customer Portal now along with a Deployment option in the Admin Image. I would certainly go take a look at those for future needs. With a little testing between now and 2013 SP2/3 you could have a an easier time of it.
I've seen plenty customers skip versions because of this as well and wait for SP4/5 when they upgrade as well as others who have spent time to streamline upgrades and do it every year.
We upgrade on an as-needed basis. We are quite likely to stagger the upgrade, so that projects underway will quite often not upgrade until a good break point, such as after introduction. Right now we are all on 2010, as we had no compelling reason to upgrade with 2011 or 2012. We will probably switch to 2013 after a suitable number of service packs. If it seems reasonably stable early on, then we will be able to upgrade everyone. If it stretches out too long, then we will have projects that are too heavily involved to switch.
Thanks All for your replies
My thoughts are along Jerry's idea, as all the machines are stilll on xp64 and are under a year old.
We only have 7 seats at this location and found the admin image upgrading from 2011 to 2012 very slow like an hour plus per machine
Anyway Cheers to all for now Don