I completely understand! One of my other bad experiences was when we tackled a famous large series by bike, again not designed for it, it was a nightmare riding through plowed fields! Plus, it wasn't a very nice area so we quit when we got to #30 and rode back down the hill, through the busy town to the car  PLUS, there were stiles at the end of EVERY field boundary, to lift THREE bikes over each time - the CO had said it was bike-able 

We've done the Etchilhampton Hill series, on New Years Eve 2010. Grandparents were staying and we were going out to lunch at one, but my friend and I really wanted to find some more caches to end the year off! We woke up at 6, by the time we got there it was 7, and we completed the series in just over an hour (maybe an hour and a half??) anyway, it was one of the quickset loops I've done, amazing considering the number of caches too - we were back in time for 11, giving me plenty of time to log the caches before even thinking of leaving for lunch!  I see what you mean about the bikes though, it certainly isn't designed for that!