You can do it right now, but should keep your garden far from the house. 6 feet or 2 metres is good. The water you add to the soil will be attractive to termites, so the further out the better (but not so far you can't nip out for a herb). If this doesn't work for you, grow your garden in raised tubs that you can see underneath.
Leafy greens will often take up toxins from the soil and some termite spray (like imidacloprid) are taken up by plants. That's good if you have aphids, but not if you have termites.
Most perimeter sprays aren't much good after 5 years, but it is still best to leave them be.