I have water-bottle cages coming loose. Use locktite?
Hmmm... shouldn't be necessary. Did you lube the threads before you inserted the bolts? Grease or a little lube on the threads in the frame or on the bolts should ensure enough tightness to keep them tight. Sometimes they get put in dry, which usually means you can't get them tight enough. If you lubed them and they're coming loose, it might be that they weren't tight enough. If they're lubed and tight and still coming loose, then you can go with a light duty locktite like green, but it shouldn't be needed.
Another point: if you were to locktite the bolts, there's a chance that it might cause a problem when it comes time to remove them, as the locktite might let the bolt turn the frame insert. That's a maybe, as I don't really know whether the frame inserts on the Cervelo are mechanically or chemically attached or both. Still, locktite would raise that concern on some frames with bottle boss inserts and it'd be a bummer if you went to remove the bolt and the insert started spinning and loosening in the frame, which I've seen on certain inserts.
Also, there should be flat washers beneath the bolt heads. Those should help keep the bolts tight, too.