The hairline cracks you could fill with caulk if they are truly hairline cracks. The caulk is going to flex while any patching compound will not. But, any crack bigger than hairline will still show if you caulk it because the caulk will shrink and the crack will not be filled. There is a certain technique to caulking small cracks...you want to lay a very small bead of caulk over the crack and then smooth it over with a wet finger. You want to do this carefully so that you do not push the caulk deep into the crack but you also want to make sure that you do not leave the caulk on top of the crack as that will certainly show when you paint over it.

Mesh tape is probably the best way to repair a bigger sized crack, but you are right in that when it cracks again and that mesh tape seperates itself from the wall, it is going to be ugly. Also, in order to disguise that mesh tape, you will have to float your mud out pretty far so doing the repairs that way can get pretty involved.

I have a differing opinion for wider cracks - skip the mesh tape. Its more of a PITA than its worth. Open up the crack, take it down to lathe, clean out, paint all surfaces and plaster edge with bonding agent,fill w/ plaster. When hard sand smooth flush to surface of wall.

I agree w/ paintable caulk for the hairlines.

The problem with the lathe behind the plaster IMO is that there just isn't always a for sure method to keep that crack from coming back. In my own house where I have lived for 10 years now, I have tried every method on the handful of cracks that keep reappearing and the only one that has worked for me so far is to drywall over the plaster walls. I am no historical expert on the way houses used to get built, but my lathe is connected to the studs with very small nails and those nails have dislodged themselves over the years which basically means the strips of lathe are just floating in the wall cavities which means they move. And, the rule of thumb is that you can't paint anything that moves and expect it to hold up long term. On the other side, I have painted many, many new homes that were built using drywall and they crack in the same place over and over as well no matter how the repair is done, so sometimes you certainly just cannot win.

The use of the bonding agent is essential - elmer's pro-bond is one, there are others - I have repairs made 10+ years ago still holding strong. I once tried to intentionally remove some of the new plaster from the lathe and it was next to impossible.

That said, I suppose it could re-crack maybe alongside the repaired crack if the house was moving or something else was going on, or if the plaster was in really bad loose condition all over.

On the other side, I have painted many, many new homes that were built using drywall and they crack in the same place over and over as well no matter how the repair is done, so sometimes you certainly just cannot win.

So true.

Yes there are situations where you can't win- didn't mean to deny that. But back to the OP's question, when I was first learning about plaster repair my plaster guru told me that in those instances it's still better to do without the mesh tape because it doesn't really stop the problem, and then the repairs become so much more difficult having to remove the mesh, all you can do really he said is accept having to touch it up every so often

Guess I have strong feelings about mesh tape because the previous owner of my house did an awful job with it - all over the house! By far the most difficult time consuming part of it was undoing her poor work.

Now, my experience is solely old plaster and lathe. Because the surface is so irregular you can do a quick easy repair and it's not going to be very noticeable at all. I would imagine drywall is a different kind of animal, perhaps same repair methods do not apply?.