Giles and
@Andrew_P - as far as sportives are concerned, I absolutely agree with you - poor value for money and rarely worth doing.
However, like you and others who've posted, most of my riding is alone, on a self planned route. And believe me, I thoroughly enjoy the route planning aspects (hangover from orienteering inclinations). I assume you have enjoyed planning (your own route) and riding an end-to-end for example - I have.
Audaxes, though - as others have suggested above, it is a nice change to ride with others on a route that an organiser has taken trouble to design (probably with local knowledge and certainly with multiple recces). The cost of entering an audax is invariably low - and actually the act of entering generates a commitment: as opposed to 'I'll see what the weather's like and how I feel' approach. As an illustration, the
Bryan Chapman Memorial 600 audax this year cost £57 to enter (iirc). Light breakfast at the start, three course meals (if you wanted) at the 200km point, the 300km point, the 375km point eat before sleep(optional sleep stop), the 375km point (breakfast), the 440km point (second breakfast/lunch) and either bunk or airbeds at the overnight (optional) stop (or at the 440km control). Food at the finish.
Good value? Well, I thought so. And the opportunity to ride with a few others, different riders for different sections but about half the distance alone (so a good balance for me YMMV). Would I have ridden the length of Wales and back that (or another) weekend if there was not an organised audax? Probably not. Was it fun? Most of the time: riding into drizzle, a headwind at dusk crossing Snowdonia was slightly Type 2, but buoyed by the 320km already ridden in good conditions. Was it a challenge? Certainly.