Ben/Will
An interesting debate.
Personally I feel that a lot of the long haul holidays have become so expensive, that if they were to be any longer, and thus more expensive, they would appeal to only a very, very tiny minority of people who are able to spend £4/5,000 plus on a single holiday, and do so every year, or even more frequently.
As has been suggested above it may be possible to offer more add-ons to existing holidays, but the issue with this is exactly what these involve in terms of planned activities, availbility of a Tour Manager etc, Also the more that this part of the holiday is organised for you, the more expensive it becomes, so that we rapidly would reach in excess of £1500 or so per week, especially one assumes, if only a small number of people booked the add on.
Because JY offer a certain amount of flexibility on flights, it's possible to stay on in a location if people wish to do so. This is of course, without a Tour Manager, and "under your own steam", but even a single room/food in a big city is not cheap. It may be possible to offer more flexibilty around the planned holiday, but JY have gone away from this recently by no longer offering "land only" prices, interestingly an option many of their competitors still offer.
When looking at holidays, I tend to look not only at companies like JY and Solos, but also at the numerous activity based holidays, or interest based holidays, which by their nature attract a high percentage of single people, and in some cases make certain dates singles only. I have to say that such holidays are often substantially cheaper than JY, and in many cases, don't offer any less meals/included activities, or use cheaper hotels. OK, many of JY's potential customers may not find these "interest" holidays meet their needs, but an awful lot do.
Unless JY want to define their market exclusively in terms of very wealthy, retired people, who aren't limited either by annual holiday leave or money, then I feel that to increase the length/price of holidays would be to lose a very substantial part of their market, and would be a gift to the growing number of competitors in the specialist holiday market
Stuart