Hairline cracks appearing in ceilings and plasterboard

pieroabcd

Hi, when I bought my house 2 years ago I noticed several very thin hairline cracks on the ceilings of the ground floor, that in a certain point forked.
I refilled them with some plaster  and didn't think about the anymore, but after 18 months they reappeared just the same as before.
Now I noticed the same very thin cracks even on the two walls, in completely different positions (they are 4 meters apart and on two separate walls).  Where it doesn't sound hollow everything is fine, no cracks whatsoever.

They are so thin that they look literally like hair, like without width.
In most cases they are  straight, but at one point they fork.

Should I be concerned? 
Would it better to get rid of the plasterboard and add proper plastering? Not that I'm looking forward to repeat what I had to do to fill the space behind the skirting boards upstairs, but if it helps...

Thanks 

pramsay13

Is it a new build? Newly plastered room? Newly painted? 
There could be any number of reasons but while still hairline they wouldn't concert me too much, only if they got wider. 

pieroabcd

100 years ago it was a new build , but yes, I repainted it 2 years ago.

Green_hopeful

Cracks happen. We have loads. I paint over them and if they come back I live with them. The normal rule of thumb is only worry if you can get a pound coin slotted in the gap. I suspect none of the cracks in your walls are that big. Ripping off the plasterboard and replastering is likely to give you more cracks as the plaster dries so I wouldn’t go there. You can get crack covering paint which might help. It has on some of our cracks. 

Grenage

Ceiling cracks on old ceilings (especially lath and plaster) can be difficult to fully sort.  You can rake them out and fill but they often come back. 

Lining paper is probably the best solution if it bothers you.

FlorayG

The last house I had was built in the 1930s and there were two very long cracks in the living room ceiling when I moved in. They were still there when I moved out 20 years later and looked exactly the same

stuart45

You can cover cracks with the tape and fill method. Pre fill the crack, then bed on a strip of paper tape, 3 coats over the top and then a light sand.
I've used this method for years at home and on customer's jobs and it's really effective and long lasting. Paper tape is better than mesh unless in a damp environment.

pieroabcd

Thank you all.