How long is it safe to leave in primary?

I started a 5 gallon batch of apfelwein about 6 weeks ago and it's taking longer than expected to finish. There is still quite a bit of activity in the airlock, about 1 bubble every 5 seconds. I measured the SG last week and it was about 1.01 still. OG was 1.06. How long is it safe to leave it in the primary? I don't want to get an off taste by leaving it in there.

If I go ahead and rack, will I end up with a sweet product? I want it to be very dry.

I leave mine in primary for 2 months before bottling.

I rack mine off to a secondary when it stops bubbling to let it bulk age. At 1.010 and still bubbling, you'll be fine to leave it in the primary for now. Also, racking to a secondary won't stop fermentation. The lees will be left behind, but any yeast that is still suspended will be eating that remaining sugar. If you're making a dry cider it's best to let the yeast eat as much as they can before moving it to a secondary.

I know I'm going to get slammed by people for saying this, but it works. One bubble at every 5 sec is a good rate, but if you notice it slowing down so that there's a bubble every min. or two, shake things up a bit! Don't go nuts, but pick up the carboy/bucket and tilt it a bit, then put it down. I've noticed that disturbing the lees a bit will speed things up. Also, don't worry about O2. Unless your airlock starts sucking back you don't have anything to worry about. Tilting it will release some trapped CO2 anyway.

A bit of a ramble but you get what I mean.