The Japanese semi-audiophile crowd (The boards at
http://natto.2ch.net/av/ constitute my samples) has been occasionally suspecting a "Sony timer" in the works. That is, Sonys may have been designed/fitted with parts that break down weeks after the (for instance, 1 year) warranty expires. This thing, for them, is suspected of Sony and only Sony.
In reality though, Sonys tend to be are as reliable as every other make, more or less, give or take. The only Sony MD product that has proven to be vastly inadequate in quality was the MDS-JA3ES, the first ES-series MD deck. There were many reports of the pickup failing way before it should (after recording as little as 30 discs, some owners have said).
In MD portables, Panasonics seem to be relatively less durable. It seems that the disc holders of their MD players don't have adequate strength, so they'll cease to hold the disc down with enough force, which makes the unit think there's no disc inserted when in fact you have loaded a disc. This is ironic, for Panasonics in other arenas are often quite durable.
To answer your question: Player-only pickups often last for a long time, much longer than recorders. I'd say your E90 has the potential to last 5 years, if not more, and suggest you don't buy a new one just because it
might fail. Because it might fail, and it might not.
A trick to extend the life of your MD equipment, is to keep it in clean air as much as possible. Smoking around your MD portable, for example, is a no-no. Some even suggest not using the cleaning disc, but lightly wipe the pickup with something (e.g. really fine eyeglass-cleaning cloth). I personally do this and it hasn't caused any harm, but do it at your own risk.
