Whether you will see ECC errors depends a lot on how much memory you have and how old it is.

A computer with 64 GB of memory is 4 times more likely to encounter memory errors than one with 16 GB of memory.

When DIMMs are new, at the usual amounts of memory for desktops, you will see at most a few errors per year, sometimes only an error after a few years. With old DIMMs, some of them will start to have frequent errors (such modules presumably had a borderline bad fabrication quality and now have become worn out, e.g. due to increased leakage leading to storing a lower amount of charge on the memory cell capacitors).

For such bad DIMMs, the frequency of errors will increase, and it may become of several errors per day, or even per hour.

For me, a very important advantage of ECC has been the ability to detect such bad memory modules (in computers that have been used for 5 years or more) and replace them before corrupting any precious data.

I also had a case with a HP laptop with ECC, where memory errors had become frequent after being stored for a long time (more than a year) in a rather humid place, which might have caused some oxidation of the SODIMM socket contacts, because removing the SODIMMs, scrubbing the sockets and reinserting the SODIMMs made disappear the errors.

>A computer with 64 GB of memory is 4 times more likely to encounter memory errors than one with 16 GB of memory.

No. Or well, not exactly. More bits will flip randomly, but if between the two systems only the total installed memory changed, both systems will see the same amount of memory errors, because bit flips on the additional 48 GB will not result in errors, because they will not be used. Memory errors scale with memory used not with memory installed.