I have a similar problem with my 968. it always starts when cold, but it cranks longer than i would consider normal. - I suspect the fuel pump check valve as AF suggested, but i have not had time to troubleshoot it, since it still works sort-of ok. I also suspect GSS (gummy starter syndrome) since it cranks slowly. More about that at the end.
On a hot start, usually it catches almost instantly, but occasionally it tries to catch, and doesn't. After that happens, i have to crank it for a good 20 seconds or more, before it finally sputters and stumbles to life. This one, i can't figure out.
Otherwise, it runs normally.
Enough with the long-winded note.
My point, if it cranks slower than you think it should, it could be GSS. The fix for this, involves disassembling the starter, and cleaning the old gummy grease out the planetary gearset, and replacing it with a high-quality grease. 968.net has a good writeup cleaning procedure.
http://65.61.16.109/forum/topic.asp?TOPIC_ID=9379