FlyerTalk Evangelist
Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: BA Silver, TK E+, AA PP, Hyatt Globalist, Marriott LT Plat, Hilton Diamond
Posts: 13,043
Any activity will reset the clock for another three years. A Tesco voucher conversion for example is quick and easy.
However, if you've had 3,000 miles sitting around for nearly three years, not added to the pile, and don't have a plan for topping up to a useful amount... you really might as well just let them expire or convert them into Hilton or IHG points.