Answer:
We are five little objects of an everyday sort. You will find us all in a tennis court.
Die without me, never thank me. Walk right through me, never feel me. Always watching, never speaking. Always lurking, never seen.
A great mysterious place that the bold have been known to journey into.
Dies half its life. Lives the rest. Dances without music. Breathes without breath.
Voiceless it cries, wingless flutters, toothless bites, mouthless mutters.
My days are numbered. What am I?