Optimal Size of Compost pile?

Is there such a thing as an optimal size?  Up until now I have had 1m (3ft) cubes of ready made bins as I was adding kitchen scraps in and I felt that contained was better.  Now the pigs eat the kitchen scraps so all I have now for the compost area is the cleanings from the chicken and goose houses, weeds, and grass cuttings (some of which are being used as mulch), and cardboard and tealeaves from the house.  An open heap would be easier to maintain but is it better?

There are minimum sizes for the pile to heat up enough to kill seeds and pests, but 'optimal' will depend on what you need.  For me it is usually zero.  The grass clippings and such could all go to mulch--sheet composting.  If the weeds haven't set seed, they to can go straight to the garden. 
The best use of the poulty litter depends on how much you have and how big your garden is and how often you clean the coups out.  But then you're more worried about having too many nutrients and not heating up to kill off seeds and such, so the size of the pile is whatevery you have.

"Optimal" depends on your goal--and your time-frame.  Open piles without food waste aren't too prone to predation, and will compost in time, but it may take a while.  Shorter if you're willing to turn it, of course.

Given the materials you mention _excluding any weed seeds_ I'd suggest something along the lines of Interbay mulching, a technique designed to enhance soil biodiversity; it's basically sheet composting with moisture regulation and light exclusion: creating a forest floor wherever you happen to be.   

With weed seeds,  you'd have to go for hot composting, which requires about 25 gallons of mixed materials to sustain the heating reaction or some intervention (tumbling, etc.). 


DSF
...new to permaculture, and still trying to wrap my head around some of the tweaks necessary for adapting the idea of permanent/synergistic with containers that may have to be moved, but composting's familiar territory!)

  I suppose big means that the compost heap retains moisture better if the climates dry.
  I put plants for my balconies into bigger pots so they don't dry out too fast. I buy those tiny cactuses and re-pot them and i water them not as much as other plants but i water them and they grow for me and are interesting its interestign to see what they do for instances i bough t a curlye one and all it does is throw out long and boring stalk like things . anothe has started to grow leaves someflower they even have spectacular flowers. Only some of them don't like being watered. rose.