[lsusaints7]

I know that PC's have an extremely short lifecycle, but what about dive computers?
When are they considered obsolete?
How long do computer manufacturers like oceanic/aeris and uwatec keep a model around before releasing a "new" computer?
Aren't they all based off the same algorithms they have been using for many years just making them more conservative for liability reasons?

I am considering purchasing one before my OW certification dive, but if I only use it two or three times a year, I might just save my money and use dive tables and pick up a used Uwatec Galileo a year from now. I just hate to buy something, just to find out I will need something better later on. Any answers and suggestions would be appreciated. Thanks.