I'm not, like, a professional or anything but I will say, from my own experience, it's pretty much safe within an hour or two for sure.
I use silicone lube almost exclusively. I actually often use silicone lube on my silicone toys. *gasp* I can't count the number of times we've started having PIV or anal sex - where we always use silicone lubes - and decided to incorporate a toy or two that also happen to be silicone.
I have never had a problem with any toys from Vixen (though I am extra careful and don't do this with Vixskin), Tantus (ditto the extra care with O2), Fun Factory, Evolved or LELO.
Do I recommend you use silicone lube with silicone toys? No. But a high quality lube paired with a high quality toy usually isn't an issue. Within a few hours, you should definitely be totally safe.
Best bet?
Do a patch test on the base of your toys with the lube you want to use.
I use Better Sex Essentials Silicone lube and ID Velvet primarily and have not had a single worry with them.
Of course, I may just be lucky but Tantus does say that Pjur Bodyglide silicone lube is okay with their stuff.
Also? Clean the toy really well when you're done, making sure to use a good soap and really warm water to get all the lube off.