hairline cracks in plastered internal walls? filler?

[steveo3002]

got a few fairly long hairline cracks in the living room plaster..was replastered several years ago

im thinking they will fill up with emulsion , or should i somehow V them out and fill them in for best results

any suggestion please

[steveo3002]

but will filler last better than if i just squidge some emulsion in em , then roller over it ?

im pretty sure they will fill with the emulsion..and its hard stuff once its dry ?