they still use electricity, which is more expensive than gas and not likely to be getting cheaper, and have you many electrical appliances that last more than 10 years also? people are approaching the whole heating question from the wrong angle. its not a matter of how you put heat into a house. its more a case of how you keep the heat in there once you have it. serious quantitys of insulation will not only keep the place warm in the winter, but also keep it cool in the summer. ventilation technoligy will now allow you to supply fresh air into a house that is heated by the warm air being extracted at the same time, so no cold draughts. solar thermal is probably the future of domestic heating. but using a huge thermal store, a cylinder than will hold probably a 1000 litres and upwards. this is very reliable and cheap heating, even in the coldest weather, but will only work if installed in a well insulated house.
groundsource and airsource heatpumps are sill just a sideshow. too much to go wrong, to difficult and expensive to fix, and expensive to fit. my money is going on solar thermal hot water, and in the future on a solar thermal heatstore.