d_D

It seems like a small job but gets to be a pain. You need to do it nearly every ride. If the grease gets contaminated it takes several injections to clean the old stuff out. It's also a bit messy as the old grease oozes out onto the bike and will attract dirt if not cleaned off properly. Also with bearings not designed to have grease injected the grease can make it past the bearing and fill up whatever is behind it, you could end up with a bb, headtube or hub packed solid with grease.
After all that you still have to overhall them periodically. Bearings wear even with a constant supply of clean grease.

I've used several componants with grease ports, they where available off the shelf years ago and always found decent seals and occasional overhalls to be much better. Unless large parts of your bike a fequently operating underwater modern seals can keep the crap out for a decent length of time.

I think this quote from the page sums it up.
Sustained underwater use like that is going to contaminate even the best sealed bike bearings. It's really a choice of overhalling, injecting grease or just replacing bearings fequently. Most bikes just don't have to fend of those conditions. My commuting bike that is used all year round and sits outside all day is likley to have less bearing contamination after a whole year of riding than his bike does after a single day.

Don't fall for the myth that you have to spend a lot of money to get decent componants. There are loads of well sealed good quality componants out there you just need to find them. Finding them is the hard part, forums like this tend to have a lot of fair weather cyclists that have boarderline obsessive maintence scedules and are drawn to flashy componants. Finding people who ride componants until they wear out and have actually worn out enough different componants to know what works is hard.