Since I've had an FTTC service, generally I've driven it to the max on almost daily simultaneous video downloads during my morning off-peaks. Although the local loop is poor, and the few speeedtests I've done are variable (though BT speedtester consistent) its performance seems consistent. Only noticeable change is that according to TBQM ave latency doubled from 9-18, presumably as interleaving introduced (as I'd expect). Could my practice be helping? If so, are speedtests themselves too transient to have a beneficial effect?
No-one was ever convinced by what I said, but by what they understood.