True hi-temp adhesives are available from aerospace and industrial suppliers. I would not include Pliobond in that category whatsoever; it's basically a shoe glue, but is widely available. The advantage of hi-temp RTV silicones is that they can be relatively easily removed if necessary later because they won't go brittle. The disadvantage is that no non-silicone adhesive will stick afterwards. Since filter holders are often made from aluminum, you have to use a silicone not containing acetic acid, or there will be a slow failure of the bond with aluminum. And that's the Achilles heel of most off-the-shelf hardware or automotive store options. Expect to pay about ten times more for a tiny tube of high temp aerospace silicone compare to a full caulk-gun size tube of ordinary stuff. But that's way more than enough. Last time I used aerospace silicones for a colorhead, it had around a 500C rating, and that was not even the upper limit available. There are also high-temp epoxies, but they're less forgiving in application, and certainly cantankerous in removal. ... I'm now editing this to add the observation that even certain adhesives that might not become flammable at a certain temperature (and halogen enlargers do get hot),
well, these can outgas under heat and time, and smudge up your dichroic filters. Yes, filters do get dirty, and color purity does get affected. I've discovered that a lot of this is due to conventional gasketing materials inside the housing. They don't use the best materials. Anything that outgasses under higher temp, or even by itself, is not ideal. And cleaning dichroic filters is a delicate operation.
Just believe keeping things in working order is the way to go. 
