Unless you get constant timing chain slap during the entire time the engine is running, dont be too alarmed on startup noise.. However, be aware that there is "wear".
As the engine oil pressure drops due to age of cam, crank, and rod clearances, the timing chain tensioner tends to take a second or so longer to pressurize. (lifters also follow in this category).
Make sure you arent running anything else buy 10/30W at the HIGHEST in these engines!( I strongly recommend 10/30W in all Nissan Engines in general unless you use Synthetics and you can run slightly lower or higher viscosity if you like.
Unless you make 300 HP, then 10/30 is more than adequate.
Anything else and your pumpability of oil (as well as longer dry starts during those critical first 5 seconds) becomes more wear on the engine which cuts the useable service life of your motor even if you are regular with oil changes. In the winter its WORSE.
Dont let anyone tell you otherwise
Getting back to the Timing System:
There have been occasions that a guide "breaks" and then you have a problem of material flying around and getting ground up in the timing gears. This CAN destroy your motor.. All that has to happen is one big chunk breaks off, and it jams your tensioner, and then jerks the chain hard enough to break a few teeth off the cam or crank sprocket.. As you know, the timing chain can slip, and then you loose engine timing. Result? Possible Piston to valve interference.. 2-12 valves wiped. If not the head itself!
Most tensioners are made of a thermal plastic.. Not too bad, but they are usually better when they are made of steel with a slab of rubberized plastic on the sliding surfaces. Those seem to last a very long time, and Nissan has used those most often in their engines. Not to knock Toyota, but a good example of a bad design is the 22RE Timing tensioners. (Sorry guys but its true) They are not very tough, and very prone to damage if you are even remotely poor with your oil changes.
Sorry to write all this horror story stuff, but as long as the tensioner at the crankshaft maintains pressure from the oil pump, you should be fine, unless you get major fragments.
In general, oil changes (or lack thereof) kills these things early or a combination of type of oil, or weight. (mixing brands of oils is a no-no for instance).
Ive heard of them running 200K easy with no issues and nominal wear on a teardown when maintained well.
But, If for some reason you are in the front cover for changing a seal, or replacing a head gasket or such, as a matter of course, spend the $70.00-$100.00 and get a timing chain and gear kit. It will come with all the hardware needed to both update the components and get you a new lease on your hardware.
Keep in mind that when replacing the hardware, the new stuff will not last as long as when you have a fresh rebuilt motor..They dont because when new, the engine has quicker startup Pressure, resulting in less longterm wear.
Another thing that can accelerate wear.. Forced Down Shifts.
If you were taught to use the clutch as brakes, you are also wiping out many other parts.. they are designed to shift UP.. You try to use your BRAKES to Stop!!
Ive met a few people that think you need to go 1-5 and do the same down.. 5-1 to stop..
Anyway, getting off topic there.
I myself would be alarmed at any chain slap.. its a early warning system. Pay attention to the sound.. If it gets worse, and gets both louder and seems to run "constantly" with a slap. FIX IT Immediately.