Please bear in mind that wood is a natural product. It is normal for it to weep, warp, crack and move. Like everything we buy these days, it all needs maintenance. The more we look after it, the longer it lasts. Our cars (even those that cost in excess of a million rand) need to be serviced, maintained, washed, waxed and polished. Your wooden bench also needs to be cared for, and as we have, and still currently are, experiencing extreme weather conditions, we recommend that you keep them in a semi shaded area, out, and away from, full sun.
Oil your bench (normal furniture oil, furnigloss, teak oil, woodoc oil) at least once a month. This helps to repel any moisture / water that may sit on the surfaces. At least once a year (preferably twice a year), wash down the set with soapy water. Fill all holes, cracks and open knots with a weatherproof wood filler, wiping off all excess and making sure it is firmly pressed in and smooth, then re-coat the entire unit (tops, bottoms, sides, and what is touching the ground) with an exterior weatherproof timber sealer or varnish, in a Mahogany tint. Woodoc Marine is the best and obviously more expensive, BUT, remember, the more you care for it, the longer it will last.