Hi GoDucks,
Welcome to the Mattress Forum! 
As you mentioned, Parklane is a member of this site which means I think highly of them and that I believe that they compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency. A forum search on Parklane (you can just click the link) will also bring up more information about them as well.
I’m assuming that you’ve already read the mattress shopping tutorial (which is the first place to start your research). The two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for, and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on all the parts of your personal value equation that are most important to you. Learning about mattresses and the componentry inside is much more important and reliable than any review you might read, either pro or con.
Outside of PPP and how well you sleep, the most important part of the value of a mattress purchase is durability which is all about how long you will sleep well on a mattress. This is the part of your research that you can’t see or “feel” and assessing the quality/durability and useful life of a mattress depends on knowing the specifics of its construction and the type and quality of the materials inside it regardless of the name of the manufacturer on the label (or how a mattress feels in a showroom or when it is relatively new) so I would always make sure that you find out the information listed here so you can compare the materials and components to the quality/durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before making any purchase.
The people at Parklane would be able to provide you with the more detailed specifics of all the layers and components in their mattresses (I don’t maintain such a listing) but as far as I’m aware all of their mattresses use high quality materials and there are no lower quality materials or “weak links” in any of them that would compromise the durability and useful life of the mattress.
Part of shopping for a mattress is finding a reputable and knowledgeable retailer or manufacturer and being able to trust the information you’re provided about their products and the advice you’re given as to what mattresses or components might work best for your particular situation, I certainly would strongly consider any suggestions that Parklane offers.
You can read about componentry and durability in the two posts I linked to earlier regarding those topics, but I think you may be a bit unrealistic regarding a mattress comfort life.
While it’s not possible to quantify how long any mattress will last for any particular person, if a mattress is well inside a suitable comfort/support range and isn’t close to the edge of being too soft when it is new and meets the minimum quality specs that are suggested in the guidelines here then it would be reasonable to expect a useful lifetime in the range of 7 - 10 years and with higher quality and more durable materials that are well above the minimum guidelines like latex or higher density memory foam or polyfoam (in the comfort layers especially) it would likely be in the higher end of the range or even longer.
It’s always more realistic to think of about 10 years as a maximum reasonable expectation for any mattress no matter what the quality or durability of the materials and then treat any additional time after that as “bonus time” because after about 10 years the limiting factor in the useful life of a mattress will often be the changing needs and preferences of the person sleeping on the mattress and even if a mattress is still in good condition after a decade … a mattress that was suitable for someone 10 years earlier may not be the best “match” any longer.
Having said that … with higher quality materials throughout a mattress and/or for people whose needs and preferences or physical condition or body type hasn’t changed much over 10 years then “bonus time” or even “extended bonus time” with higher quality/density and more durable materials like latex or higher density memory foam or polyfoam or natural fibers is much more likely than with less durable materials.
Phoenix