hi! I have been running for around 3 years now but only been doing races for the past year. I love Half marathons as i find them a challenge. I do also enjoy the 10 mile and 10k races. Anything with the aerobic experience without getting anywhere near the wall! You seem to be training a lot! I run about 25-30 miles per week. I do not do any of the 'interval' training etc. and do not (yet) belong to a club. I'm still able to run a sub 1h30 half which isn't too bad! I'm not sure how relevant your long run is to 10km but it will no doubt build the aerobic strength of your legs, and if you enjoy it why not! I guess for 10k the last k or so needs to be flat out. Running fast 5k training runs will probably help your time. Many people refer to the 10% rule... Try increasing either your speed or distance by 10% each week as any more will not let your body keep up with the extra stress. Your body will use quite different metabolism for a 10k (90% aerobic respiration of Glycogen/Carbs) to a longer run (15 miles will be shifting towards marathon metabolism of a higher proportion fats and lower proportion carbs). Hope some of this is of interest.