A family member recently asked for my opinion about an article from Wired that urges readers to go out and buy new Philips LED bulbs (the subtitle is "Officially too cheap to ignore").
You absolutely can if you want to. There is no downside to doing it (excepting figuring out the best way to dispose of the old bulbs). However, the upside is probably smaller than you imagine. My advice would be to buy new LED bulbs as your old bulbs burn out. Prices will keep going down, so there is no need to rush out and buy them now (plus, newer models of LED bulbs are getting better for enclosed and recessed lighting fixtures).
The average home uses 5-10% of their energy on lighting. Unless you have a large number of bulbs that you are using very, very frequently, I would not expect any noticeable savings on the energy bill.
Much more of your overall energy use comes from heating (anywhere from 35 to 50% from the estimates I've read, see graphic below). It would be much better to focus on more efficient ways of heating a room than to focus on lighting.