Timing Chain Noise '85 380SL

[tullheinz]

Car has only 87K miles, runs very well and is only used during the summer months. Occasionally (maybe 25% of the time) when starting engine I hear a brief metallic "clack, clack" noise from engine (I assume timing chain). Noise will only last less than 10 seconds. Since the noise does not happen on every start and disappears in seconds, is it a reasonable assumption that it's lubrication related?
I gather from checking other posts, noisy chains are not a surprise on these cars and repair of guides and/or replacement of chain is a major and expensive task. At what mileage do I need to worry about the chain breaking ? Is it ok to just live with the occasional noise at start up unless it gets to the point when it happens at every start and last longer ? Any other warning signs I should be aware of ?