Re meniere's disease: if sensioneural hearing loss steadily improves and does not fluctuate down again, is this likely not menieres?

Yes: As a rule Menier's disease being degenerative in nature should not improve substancially

Meniere's disease: No- Ménière's is a diagnosis that requires a careful evaluation of the symptoms over a relatively long period of time. Sometimes, the disease can go inactive, thus the fact that you're hearing loss doesn't fluctuate, doesn't mean you don't have Ménière's. Testing is limited to audiometry, ENG, and ECOG. See ENT every time you have any aural pressure, tinnitus, vertigo, and changes in hearing.