As has already said if you develop flu like symptoms in the near future then make a point of seeking medical help. Apart from that I would not worry about, it I know a number of people who have been getting ticked on a regular basis for many years only one of whom has ever developed mild symptoms of Lymes disease.
I had seven ticks attached to me last week and five the week before.
It is best to try and avoid getting them in the first place, ie tuck trousers legs into socks etc and carry tick tweezers if you are going anywhere that they are common.
The length of time they have been attached should not matter to much what you need to try to avoid is them re-gurgitating any infected blood from another animal. This is why you should never try to burn them off, smother them with a cream or any of the other supposed great ways of removing them.
Use the tweezers and grab them as close to your skin as possible, gentle but firm
and twist slowly. This is the best way to make shure you dont leave the infected mouthparts in your skin and that they spit out.