How can you say an inflatable is too soft or too firm?
It’s always nice to get something new while at the same time it’s sad to dispose of a device that has served you well. Over the lifetime of your inflatable its performance characteristics can change dramatically.
Water, sun, traffic, staff handling, dirt, pavement, tears, and more affect the life of any inflatable device. With all these elements over time inflatables become increasingly softer. Your manufacturer designs your inflatable to work with their recommended blower and the future ASTM standards will provide testing standards that will allow for testing consistency across all manufacturers to help determine what is too soft or too firm?
With your existing inflatables try to get some perspective by opening a new inflatable and see how it deflects with weight. The best way to do this would be to find the maximum allowable weight allowed for that inflatable then double that weight and place it on a disk 15” in diameter. Put that disk in the middle of the inflatable and measure the height of the disk above the floor. Then place that disk between 24” and 36” from the wall of the inflatable and measure the height above the floor again. Your test weight should not touch the ground at the bottom of the inflatable.
At the same time, if this weight does not cause a deflection then your inflatable is definitely too hard.
Use the performance of new inflatable as your guide. I also recommend that you make a video recording of your test and use it for future reference. This is only a guide but its important to keep your devices in good working order and to talk to your supplier if you have issues or repairs to be made.