If what you are describing is: Before, it would consistently crank for 2 seconds before starting and now it cranks for 3-4 seconds before starting, then yes, mine did the same thing and it can be indicative of a problem. There is now a PSB out on this exact symptom and it indicates you are getting air into the fuel system.
In my case, the lift pump was also slightly noisier than normal. I should have had it checked when I noticed it but I blew it off. 1 week later while towing an 8K trailer through NY state, the truck stopped running and left me stranded on the highway. Ford first replaced the lift pump, which got the truck running, but it still ran rough and was getting air into the system. They discovered there are pressed in cups in the heads under the injectors that were allowing combustion compression air to bleed into the fuel system. They replaced the cups and all of the injectors at the same time. Runs perfectly now and starts fast like before. They think getting this air into the system may have caused the lift pump to fail prematurely, or it may have just been a coincidence.