Sprung edge bases feature a complete spring unit on top of the
base giving a softer feel. Considered the most luxurious option,
they provide even more support across the whole mattress and act
like a giant shock absorber, increasing the mattress's durability,
but this should not cause the mattress to dip. 

The mattress is the heart of your bed and the part of the
purchase you should spend most time and money on. The secret of
having a good night's sleep is the mattress and bed base you
choose. Always remember that a 'bed' is a mattress and a base
working together, you should not consider them in isolation and
should ideally always try them together.  We always recommend
you buy them together because the two are designed and manufactured
to complement one another in terms of support.  Your mattress
may show visible signs of wear and tear but the base will have had
equal pressure and strain - it just doesn't show quite so clearly.

Putting a new mattress on a base for which it was not intended
or putting a new mattress on an old base can impede comfort and
reduce the useful life of the mattress.