How many of you adjust your own valves, and how often?

I haven't done this since the mid 1970s on a Datsun 240Z, and it could be done with standard mechanics' tools because the SOHC operated the valves using rockers. All my cars since then have had hydraulic tappets, requiring no adjustment. According to the FAQ, the 740's valves can only be adjusted using special tools and special shims, like a Jag or Ferrari.

The 740 I recently bought has about 470,000 km on it, but runs reasonably quietly, with no alarming rattles. I have the original maintenance record book up to 240,000 km plus a notebook and some receipts up to the present time. According to the owner's manual it looks like valves should be adjusted every 30,000 miles (48,000 km), so I presume the dealer service done for the original owner up to around 180,000 km included doing the valves, even though it's not mentioned. However, there is no mention of valves in any other entries up to the present time, even though trivial stuff like filters, plugs and oil changes are noted, and of course, bigger stuff like brakes, suspension, water pump, timing belt, etc.

So, what I'm thinking is that the valves were never adjusted in the last 290,000 km (180,000 miles). I don't think that's such a drastic assumption, because nobody adjusts valves these days except on motorcycles, or when they have their high priced mechanic do it on exotic imports.

Okay, my question is, do my valves need to be adjusted ASAP to avoid imminent disaster, or can I put it off until I get around to it? Also, is the 30,000 mile interval critical, or do you let things slide once the motor is past 180,000 miles? What is the flat rate for adjusting the valves by a shop with the right tools?