[Arran]

Bill;
When you have electrically restored as many radios as I have you learn that there are only two types when it comes to the old paper capacitors, there are those that have failed and there are those that are failing. With regards to drifted resistors causing no ill effects it depends on the circuit, a drifted bias resistor in the audio output circuitry can not only cause distortion but cause the power output tube to draw too much current, a drifted plate resistor can cause a tube to perform poorly or not at all. I know that troubleshooting that bad component is what most old TV and radio repairmen had drilled into them decades ago, you could use that approach when they were 10 to 20 years old but you can't really use it now that they are 50-60-70 years old.
If you have followed these forums with any great regularity you will see there are some of use that go to great lengths to restore a set with new parts and still have it look original. Techniques like restuffing the old capacitor shells, Bakelite blocks, or even casting reproduction dogbone resistors, reproduction cloth covered wire, and speaker reconing, keep the set looking original but playing like new. If you are happy to have shelf queens that you can mostly only look at that's your prerogative, but I for one would prefer to have something other then a glorified book end or plant stand.
We are not taking about hot rodding or modifying anything, in a Model A for example, do you think it makes the car more original to run it with dry rotted tires, belts, and hoses or tattered wiring? Those items didn't leave the factory in that condition and they were intended to be replaced as then aged and wore out, just like capacitors, tubes, and resistors. I would rather replace all of the drifted resistors and leaky capacitors in a set then risk damaging something more expensive or difficult to find item like an oscillator coil, a pot, or a power transformer. This is also not 1953 where you can call up your Philco parts distributor and have them in your hands within two weeks, I would prefer to keep the hard to find original parts and toss the easily replaced ones. I also don't feel like taking a set apart six months to a year from now because a 50 year old paper cap decided to die. It's because most of these sets do not work that many people do not see the value in them as anything other then a Ipod dock, guitar amp case, or a liquor cabinet. If they could be shown that they can be made to perform as well, if not better, then a modern radio and put to practical service, I believe that many more will be saved and live out the remainder of their existence as what they are, radios.
Regards
Arran