MSPeconomist

Perhaps instead of insisting on a FF program where miles never expire, the OP should look at those with rules saying that miles don't expire if there's some account activity and look carefully at the rules regarding what activities keep the account alive.

Instead of scattering miles over different programs, the OP could start by thinking about what alliances have service he/she likes and convenient flights/connections to places he/she travels. Then within that alliance, compare different FF programs. The thread title indicates that the OP is focusing solely on SkyTeam, but perhaps this decision should be re-evaluated at this time. It's not obvious to me that SkyTeam is best exTLV, although DL does have a nonstop to the USA, plus connections on AF/DL through CDG and KLM/DL through AMS. Through these hubs, the combination of AF and KLM seem to cover Europe and in fact the world pretty well.

Going with oneworld would mean BA connections through LHR all the time, although there might be some IB possibilities too. *A would mean primarily LH/LX, but some nonstop service to/from USA on UA, northern Europe and connections on SAS, etc. If the OP anticipates travel to other areas, such as Asia, there would be additional considerations.