I had the shim made up by T&L Engineering as a single item, when they were sorting out the first 'ahem', to avoid that wafer-thin shims thing Richard.
Chances are after so few miles your other bits will be in good shape I'd have thought. The needle-roller conversion is assuredly a good thing, but to be honest, I've done a lot of miles on my engine, not treated it especially kindly (or unkindly), and the timing side has held up well. What I don't do much of is 'down to the pub' type riding, most runs are an hour or more non-stop which does reduce wear per mile, and always under light load until things are nice and warm. And nor do I run at Musky speeds!! - 60-ish suits me just fine on non-4-lane roads, it"'s only a Flash-spec engine after all. If I'm in a hurry i'll go a bit more quickly, but again, under 70.
The only time I was really pressed - about 3 months back - I had an exhaust valve seize at 75-ish on a dual carriageway, which was very noisy, inconvenient and required a van to rescue me. My own fault, I'd made a new lh exhaust valve guide when I had the motor apart to do the crank thing, and must have been too mean with the clearances for when things got good and hot. That'll teach me. Luckily, despite the pushrod leaping out and the piston ramming the valve shut again (well shut!), causing huge flames back through the carb and near enough setting it and me and the battery alight, it all survived and has done an uneventful couple of thousand miles since then. Tough beast, I reckon, and as reliable as ever, warts and all.
Here's hoping you haven't got any other nasties to deal with apart from the mainshaft and the race. Bill