When should one take a training break?

And for how long....

Having started regular swimming 11 months ago, (I was never competitive), I've gotten into open water racing. I've become quite obsessed in my training, but while trying to learn more about that, I'm also wondering about taking breaks? I've overtrained a few times in the last year, and have learned my lessons, my training incorporates different types on different day to allow recovery, with regular periods of 2 to 5 days off (work, rest,colds etc). I was doing 3 weeks usual with 5 days straight off then starting again.
But it's more mental tiredness. The last few weeks have been harder (though still ocassional good days) but I've read it's detrimental to training in some areas to take more than a week off. I'm 44 btw but have to force myself to remember that..
Training is usually 5 to 6 days a week, about 25km per week (in the pool, too cold for the atlantic yet).
Thoughts?

Regards
Donal
Ireland

Another way to look at it is 5days/week with workout monday, tech on 1-2strokes tuesday, workout wedsday with some dryland included,thurs tech 1-2dif stroke tech work, friday do some fun stuff mixed with some fast stuff have friday as a kinda depending on how you feel day. with at least a little workout in there. That will keep you going and probably enjoying it.

Thanks guys, for all the answers.
I like the idea of a structured week, though I find it hard to move away from lots of endurance work.
Example: yesterday, (I was very tired and did an exceptionally short ) 45 mins. 15 mins technique, then 100s x 10 off 10 secs at 1.15 then some aerobic to finish.
Today, I did my usual 15 minutes pulling to start, then 45 mins of aerobic distance with 200m sprint every 5 minutes (it's usually 8 minutes, but I had a coffee about an hour beforehand so was feeling good, performance enhanced..!). Tomorrow will be either 50/60% endurance EN-1 or mixed with more sprints. Sat/Sun are usually a long 1 1/2 hour endurance & a 1 1/2 hr EN-2/EN-3, then monday a slow one again to recover.
So I've been learning to mix what I'm doing each day, but haven't structured it specifically,as I kind of decide each day based on how I'm feeling and what I did the previous day.
All this more specific training has really only happened in the last 6/8 weeks. Also, much of the training routines I've read seemed designed (unsurprisingly) for pool swimmers, i.e. up to 1600m, whereas I'm aiming for open water where races start at 1 mile, but this year specifically aiming for the 3 to 8 mile range.
Pulling for me has been about teaching myself proper technique rather than extra loading, I didn't realise to do that so much..
Kicking is a different matter. While I do it maybe 2/3 days a week it's never for more than 400m. This is because I had to learn to kick less for open water as I previously kicked too much and also because it's soooo boring.
As for CORE work, I'm afraid I confess ignorance. I'm not sure what you mean.
On my pulling I concentrate on my rotation, reaching (not reaching enough is a flaw caused both by years on a surfboard and also sea swimming), hand entry position, high elbow and glide.

My biggest problem is prob. complete lack of advice or help, as there's no Master's club anywhere near me. I had to build my stroke from scratch and it took me a long time to start to get that water "feel" you talk about (6/7 months), which I didn't realise that until I started to feel more "fluid" in the water, pardon the pun.

Also what is "fun stuff"? Okay, I love swimming even in the pool but because it's my target for this season that keeps me going. "Fun" has been one of those days you know when you get in the water and you;re completely loose and comfortable and making time, maybe keeping my endurance speed pace goal for 45 mins before it starts to slacken. And they only happen occasionally.

(As for location, I live in the SE, the Atlantic covers 3 of the 4 coasts. Kinsale is home of the Sandycove swims and annual Challenge, a great location for sea swimming with a 2km circuit around a small inshore island, I'm about 1 1/2 hrs drive from there.)
I laughed when I read tri-athlete are allowed wetsuits when water temp less than something like 68 F, which is about 11 1/2 months of the year here.......

Regards
Donal