Hi Tradernick,
For the majority of people … with careful testing (using the guidelines in the tutorial) their choice will generally be “close enough” that if any fine tuning is necessary it would be relatively minor and involve different mattress pads, sheets, mattress protectors, or perhaps even a topper if their mattress is too firm (see post #4 here and post #10 here).
For those that are more sensitive to smaller differences in a mattress and/or are closer to the “princess and the pea” than the “I can sleep on anything” end of the range or that have more challenging circumstances or a history of choosing mattresses that aren’t very suitable for them then 7 days of “real life” sleeping would provide a more accurate indication than testing in a showroom and for the large majority of people would be “enough”.
There will also be an initial break in and adjustment period with any new mattress (see post #3 here) that can also affect how the mattress feels over the course of the first few weeks so for an even smaller minority of people that are more sensitive yet this can also affect how well they sleep on a mattress and for this much smaller minority 7 days may still not be enough to really know for certain how well they will sleep on a mattress over the longer term.
Phoenix