You never EVER move the OM.
There is nothing worse then rushing hummies and almost taking them out when I moron decons OM to move it and you can't evolve to finish off hummie base.
You shouldn't move without asking first. The whole reason to move OM is to be in control of WHEN it is down. You don't want to let humans decide when that happens.
Aliens structures do not need the OM to be in close proximity to work. They need only eggs.
That doesn't change the fact that you don't want OM to be destroyed since A) your defence stops working when OM is down and B) you can't evolve when OM is down.
Pick a good spot to build and build an egg, then the rest of the base. Feel free to leave the OM unattended and let the hummies take it. Once it's down, THEN build it at the base location.
If the human team isn't really stupid they all attack when they hear "OM is down". They then have a good chanche to find your new base and destroy it before OM and the new base is functional. I agree with that it's usually better to move the base before OM, though.
Hummies flock to OM as flys to shit, so often it's better not to have the OM in base.
When OM is down base defence stop working. OM also worth alot of credits (500?). If you can avoid it, don't give humans that gift.
Also, aliens do not benefit from "bases". I hate to see 2 eggs and rest of the points is wasted on tubes and baricades.
One nade and Tremma with a PSaw will take it all down in a few seconds.
If the tubes is placed in such way that you can destroy them with one granade that's a sign of bad base construction. If you can't construct a good base, then it's better not to. Of cource aliens can't benefit from badly built bases.
The alternative to build one base is to hide alot of eggs. The problem with that is that if a human finds an lonly egg he gets 150 credits for destroying it or worse he could spawnkill until humans reach the next stage.
For most maps I prefer one wellhidden egg and a wellbuilt base (with OM in it, othervice you can't say it's wellbuilt). Transit is one exception from this rule.
Reagards,
MtS