It depends

The perennial answer of r/askhistorians.

I'm going to tackle the Germanic tribes since that's both where I focus ,and also because a full run down of all these societies would be far beyond my abilities.

If I understand you correctly you want to know how long indigenous religious practices remained after conversion to Christianity. Not counting syncretic practices. Unfortunately it's a little hard to answer because these various religious traditions cannot have straight lines drawn to pre-Christian times.

There is an idea that religions before Christianity were immutable and universal within their followers, and this is not the case. The Norse in Iceland would have had different practices and beliefs from Norse living in Kiev, and both would have different practices from Anglo-Saxons in 7th century England. These practices were constantly changing and adopting other customs from other cultures throughout their existence.

Certainly some commonalities can be drawn, but even in Anglo-Saxon England there were wide variances in things like burial customs, inhumation vs cremation, amount of grave hoods and what they were, and so on.

However fear not, I can answer you in regards to some clearly pagan practices. Christians were able to recognize certain practices as incompatible with their religion and we can see that once the evidence, scant as it may be, leaves the historical record these practices can be said to have died out.

An excellent example of this is horse consumption in Germanic societies. It was a practice condemned as unchristian by St. Boniface in his missionizing, and it was actively repressed in many societies. Kristopher Poole attributes the sharp drop off in evidence of horse consumption in England shortly after conversion to such prohibitions. When combines with textual evidence from Bed about conversion in England, it seems that the repression of horse consumption was quick and effective. Evidence for horse consumption only ticks back up centuries later. The practice was seemingly eradicated in the span of a generation or so.

If we want to use horse consumption as a metric for pagan identity, which I believe we can, in England at least, conversion seems to have been relatively quick with horse consumption dying out in the span of only a few tens of years.

Now this is only a snapshot of one practice in one area, and someone more familiar with the other regions and cultures you brought up can always chime in, but at least in Germanic societies, conversion was fairly rapid, and indigenous practices died off relatively quickly.