Probably …not it's safe but… because your surfaces have changed color over time (they always get slightly darker from exposure to light, dirt and from heat and moisture)…even if you wash them… the 7 year old paint might not be good either… if it's acrylic it might have lost it's quality for adhesion… if it's oil, you'll find a nice skin of hard surface over the paint after you open the can… pry it up, discard it, stir the rest and you can use it… but it surely will show unless you paint an entire wall or ceiling, (instead of "spot touch ups")… which is advisable regardless of what you finally decide to do…