Hi,
The cache will become a performance issue. If you find that the machines serve their requests fast enough without the caches, then you're lucky. They make a big difference. Under load, you might see the database struggling unduly as a result. I'd say that it's a workaround until you get the EHCache clustered. You can copy the ehcache-default to <extension>/alfresco/extensions/ehcache-custom.xml. It will be picked up as the default automatically. Then follow the instructions on the EHCache site. Once you've done it once, it's done and will be worth the effort. I want to make that config a single switch, but it'll require some low-level hooking into EHCache, so I've not had time, yet.
I'd also say that you should make the index recovery task fire more frequently. 5s or 10s at the most. Just as long as it is on remoteOnly, it will not affect your system noticeably.