I grew some Sedum spectabile 'Neon' and it flowered very well, but the flowers do not last very long. I would like to extend the flowering period. I noticed a scattering of rebloom, but it was not very good. Could I force a consistent rebloom on these?
As far as I'm aware you can't "force" a consistent re-bloom.
Such Sedum's have a relatively short bloom period, very late Summer through to mid Autumn (Fall) at the latest. Yes they look spectacular (at least I think so) when in bloom, but the "late" flowering season means there's very little chance of a re-bloom.
The best I think you can do, is plant them in the preferred location ie Full-sun in well drained soil, then enjoy them for what they are. Personally I think their foliage is striking, at least on certain varieties, especially the ones that have variegated leaves, and the purple/red foliage varieties...
Maybe one way to extend the bloom period (though I've not tried it) would be to protect them on nights when a frost is forecast or when temperatures are getting down close to freezing...