Hohn - Unless you severly over greased them you should be fine. A little extra won't hurt,as long as it didn't damage the boot.
The lubed for life stuff is usually pretty good. Due to the fact it will never be greased they usually have a large polyurethane boot,that is well captured around the joint. They are also filled with good synthetic grease. They can also use a tighter tolerance bearing\bushing design,as it doesn't have to pass grease.
The older style joints have a boot,but it doesn't always seal completly,and water and crap gets in and ruins the joint.
Same holds true for u-joints.
The lubed for life stuff is actually more expensive for the mfg's to use on a new truck,but they pay off in the long run as they don't have to replace as many under warranty,and the customer is happy as his truck goes further with fewer repairs.
It's hard for us guys,as we want to make sure everything is lubed,and tend to over maintain things sometimes. We tend to get upset when we can't do anything with them.