Old data point: We spent the majority of 1975 abroad on a single trip. I have no memory of customs upon return which would indicate it wasn't anything notable.

In 1981/1982 we spent about 12 months abroad, again a single trip. This time I do recall that it wasn't an issue at all even when the first thing the customs guys saw was accidentally-packed contraband. (Seeds--the suitcase had been packed under a tree and we didn't notice it add a seed pod.)

Since then I haven't been out of the country for more than 3 weeks.