would a standard relay burn out if it was being switched at, say, the same speed as indicators?
my first thoughts are yes.

cheers

It would eventually fail, but it depends on the kind of currents and voltage it's switching whether the contacts fail before the actual mechanism.

as mike ^^^^ pointsd out, the question is a little bit vague.

bear in mind that modern inidcator units and those that are for LED light have a relay so you need to be more specific as to what it is you are angling for.

Indicator flashes aren't fast in the grand scheme of things and flashers are just specialised relays anyway.
They are specified for a minimum number of cycles - typically around a million for a quality relay.
So you won't burn one out if you stay well under the current/voltage rating unless running continuously.

Here are the Bosch specifications for their relays.
http://www.bosch.se/content/language1/downloads/Relays_Catalog_2005_2006_eng.pdf

At a million cycles and 1 cycle per second you will get 11.5 days before going out of spec, not a problem for indicators where you maybe have 100 cycles per day and get 10,000 days.
If you want constant operation then you're looking at a solid state, probably mosfet, solution for long term operation.

Won't be a problem as long as you keep within spec. As said 1 million actuations minimum is non uncommon. Which is a hell of a lot of indicating. And relays are cheap as chips so when you get to 1 million actuations just replace it

A standard relay won't switch without an input, so what are you trying to do?
If you want to run indicators from a relay you will need to use a standard toggle switch very quickly.
If you want to run high powered indicators, why?
If you want to make blue lights or headlights flash like the plod, you would need a flasher relay to actuate the relays.
You could rig it on the bench.
I am curious, what do you want to do?

im just trying to sort out some rather funky wiring... got some non ford stalks, that have tiny wires coming out of them, so not happy putting the indicator supply through them, i recon itll kill the stalks. so was thinking of putting relays into the system so the flasher relay goes to the stalks then switches a relay on the indicator feed... hope ive explained my thoughts okay!