Very important for an indoor field, size and multi-level. Unless it's a couple if buddies just muckin' around, 10,000 square feet starts to feel like a garage quickly.
Also what Brian said, change it regularly.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē