I have been one of those, but honest one, devoting quality time wholeheartedly; who pioneered and was learning a foreign language. So the best way is to surround yourself with people who speak the foreign language alone (not mentioning the language coz of identity issues, still kinda PIMO) . I worked for 6months and went for 6 months at a time. it was frugal living but enjoyed every minute of it helping many to come into this cult (unfortunately). Many are pioneers themselves now and are even serving where the need is greater like I used to. Still get emails for tips and suggestions.
Yes many can be doing this for their own needs as you so mentioned, yet there are those who wholeheartedly give their all for the Lord's work.I personally know quite a few too. It takes all sorts.
Zing