I used tanglefoot not vaseline, though I see no reason why vaseline would not work similarly. Both never dry out.
Tanglefoot works, but I stopped using it because:
* it is a sticky mess, and hard to apply without making a mess (even wearing gloves)
* any place that branches touch the ground or other trees ants will find a path in anyway. If you have an outdoor orchard you could avoid this but in a dense greenhouse it is impossible
* I read that applying tanglefoot directly to the trunk can harm the tree, so I put painters tape on first. BTW, I strongly recommend against every using masking tape for anything because it is worse than painters tape in every way and only the tiniest bit cheaper
* tape applied around a tree trunk is surprisingly strong to the point I worried it was constricting the trunk as it grew. Within a couple months it seemed overly tight. You could vertically score the tape but then you have to worry about damaging the trunk and introducing disease
I am glad you brought up this post though because I have some trees I care little about and I want to try applying tanglefoot directly to the trunk and see if it causes any harm. If it is harmless I may go back to using it.