Dunno but I'll try one to hear how it affects the nodes.
Hleeid, the amount of "sag" from orienting a woofer either face-up or face-down can be calculated based on the woofer’s moving mass (mass of the cone & voice coil assembly) and the suspension system’s compliance.
The woofer in your subs will sag about 2.3% when it is face-up or face-down. So you theoretically lose that much of the otherwise available linear excursion.
However your woofer will not exceed its linear excursion unless you hit it with a full-power sine wave at or below 16 Hz with amp’s the protective 18 Hz subsonic filter disengaged and the port plug removed. If either the subsonic filter is engaged or the port is plugged, your woofer will never approach its linear excursion limit. In fact with the subsonic filter engaged it will never be asked to move even one-half of its linear excursion limit.
As far as the longevity of the woofer goes, my understanding is that it will be unaffected, that the suspension system doesn’t wear out faster nor does the sag increase significantly over time. This is based on a conversation with a woofer designer for a major prosound loudspeaker manufacturer.
I made a custom speaker for a customer about a dozen years ago that used the previous version of that same woofer in a down-firing configuration. He and I crossed paths again on another forum a couple of months ago. He has had no issues.
However if you want to play it safe, you can rotate the sub 90 degrees so that it’s lying on its side.