I've used Threelac for years and more recently Fivelac when it became available with great results, but unfortunately I normally make the mistake of 'opting out' of the maintenance dose (recomended you continue to take one straw per day even when you feel really well). This means that I gradually get to feel worse again and one day wake up and think - I need to order some more fivelac + bio-kult and get things back on track.
I never realised until recently that the good guys in 3 / 5 lac don't live in your gut and need to be topped up regularly, so it looks as though I will have to have more discipline in future and continue with a low dose even when I feel good again.