When is it time to buy a stock? One of the best-known pieces of investing advice tells us to buy low and sell high. But what constitutes "low" is relative. A stock near its 52-week high can still be considered at a "low" point, provided there's plenty of upside left. That's why investors shouldn't ignore such stocks.With that as a backdrop, let's look at two companies trading near their 52-week highs and are still worth buying: Abbott Laboratories (ABT 0.20%) and Netflix (NFLX 1.04%).1. Abbott LaboratoriesA ...