If you intend to credit LH flights to TK be careful as P fares in Business Class earn nothing (not sure what Economy fare buckets are like).

I’ve found that TK status is very easy to maintain. 25,000 points in one year or 37,500 in two years. As an Elite member flights from Europe to the Far East in Business Class earn 20000 + depending on the exact origin and destination so a Business Class trip a year would be enough to maintain status (I’d imagine the US wouldn’t be too much different to this).

In terms of spending points I find TK expensive unless you get saver availability when I find TK can be very good value.