I'm a big advocate of fenders and I leave mine on year round. I've done some modification to my SKS P-45 fenders to make them even better "full coverage" than standard.

Mudflaps, front and rear. The front one covers down to within 2" of the ground and keeps road spray from getting on my drivetrain and, more importantly, my water bottles. The rear one keeps me from spraying fellow riders as I pass.

Modified hangers/attachments. A fender does very little good if there's a huge gap between it and the tire. My CX frame has bigass clearance up front and a tiny (by comparison) 28mm tire, so I extended the crown hanger by 0.75" to tighten the fender along the top of the wheel and reduce forward spray from just flying up and back at me. I put a spring loaded attachment at the chainstay bridge to allow for a tight fender line but also allow for the fender to be pushed toward the bridge for wheel removal during flat repairs. (the peril of tight fender lines and semi-horizontal dropouts.)

Lengthened front extention. I took a section of a broken fender, trimmed it to appropriate length, moulded it using my trusty heat gun, and pop riveted that sucker to the leading edge of my front fender to extend the coverage below the horizontal tangent to the wheel. The problem, as I see it, with most plastic fenders is inadequate length. Metal fenders on old constructeur bicycles were freakin' huge! Rear fenders which covered from the chainstay bridge to below the hub bolt in the rear. Front fenders which covered 160 degrees or more of the wheel, catching spray well below the bottom bracket and directing it forward and down to keep road spray off the (commonly) fender mounted or rack mounted headlamps.

Just to qualify these statements with some perspective: My commuter is also my brevet bike. I also like barcon shifters, wool jerseys, waxed canvas bike luggage, leather saddles and generator lights. So, my opinion my not sit well with people outside of the cranky retrogrouch randonneurs' club.