Will unpainted plaster become water damaged?

Question

We have had our bathroom done recently and the builders plastered one of the walls, then fitted the sink and toilet.

I am now going to paint the walls myself, but I'm concerned about the plaster behind the sink and cistern.

Should I remove the sink and cistern to paint behind?
If I leave those hidden bits of plaster unpainted would they suffer from water damange over time?

(It feels wrong to pay someone to fit a bathroom, then immediately take out the units yourself)

Answer 1

They will not suffer from water damage unless water gets back there. Normally, that shouldn't happen and there are millions of installations with no paint behind toilet tanks and sinks with no deterioration. But it's still up top you if you want to make absolutely sure.