When marathon training what day do you do your 2nd longest run, Thursday?

When marathon training what day do you do your 2nd longest run, Thursday? I usually do minimum of 10k on a Thursday but no sure if this is too close to my long Sunday  run thats now getting over 14 miles and will increase each week whilst training for the London Marathon? 

 I know some people don't do a 2nd long run and have 3  weekly runs then a standard long Sunday one.

What plans you guys following for a 4 hour time?

I do it on a Wednesday, but my long run is a Saturday, so it's the same really. How far do you go in proportion to your long run? I would be doing between 7-8 now and 10-12 3 weeks out.  What else do you do inbetween the 2 runs?

I do a 4 mile tuesday that Ill increase every 2 weeks, I dont really follow a plan but want to get under 4 hours.

I'm following the Pfitzinger & Douglas plan (upto 55 mile version) and this includes a medium long run on the Thursday plus the traditional long run on the Sunday.  If you're not recovered from a Thursday run by Sunday, then you need to slow down your Thursday run!  

I usually leave a day in between as a minimum. As to when I do it depends on when I do other sessions. Today I did 14 as I felt like it, and will probably do my long run on Fri or Sat am. Between now and then will be looking to do a tempo run of 10m in total with 5 - 6 tempo miles

I think part of it depends on what you are doing with your long run. When its a long slow run I will even consider a medium long run (MLR) the day before. But if the long run is progressive / fast finish paced I make sure the day before is very easy.

Ummm...

Sunday ---- Thursday = 4 days
Thursday ---- Sunday = 3 days

Unless you start specifying which time of day you go out for a run (and even then, arguably the most important element in terms of rest is the number of sleeps), how can your two longest runs be any better spaced apart?  As long as you've got a couple of days either side of your biggest efforts, for both muscle repair and refuelling, I think you're fine.  Whether you do a mid-week "semi-long" effort on a Wednesday or a Thursday would depend on what the rest of the week looks like.