Yes I have an assortment of relatives who emigrated and then returned. It was more common from the US and Canada than from Australia or NZ, presumably because of the cost and time issues. My observations suggest that if you emigrated in the 1700s and early 1800s it was normally a one way journey, but by the late 1800s and early 1900s, the journey times must have been reducing, sailings become more reliable and a bit more comfortable, the fares becoming more affordable presumably reflecting increased prosperity, and I start to see people coming back, sometimes on more than one occasion.
Difficult to pinpoint any single reason. I have one relative whose wife died in the US when he was about 45 and who returned to Ireland shortly afterwards, where he too died soon after. Ill-health and no-one to look after him in the US? Another worked in Canada for 15 years, and made a 3 month visit home in the middle before returning for good around 1918, having made his fortune (not really, but he was perceived as better off by the rest of the family). Homesick?
The older you are when you emigrate, it seems the harder it is to settle. Then there must have been issues to do with care for elderly parents, or inheriting the family farm and no-one else to run it. Whilst some emigrants obviously did very well when they emigrated, there must have been some who failed and who decided that going back was the answer, assuming they could afford it.
Elwyn
