“keeping the links panel open slows down indesign” is valid.

how much it slows down indesign is a factor based on the location of the files and the speed of your network.

I learned this the hard way when I first started working for my current company. I would be given files created in a different city with absolute links to files on their server instead of relative links to files in a sub folder. InDesign would run like a pig when the links panel was open and it could take forever to do even simple things like scrolling with the panel open. The program would go back to normal speeds when the links panel was closed.

My solution was to never work with remote links any more. I had to change the way we did things a bit, but it was totally worth it.

As far as the 300dpi, i think still think it's the “safe” rule of thumb, absent any knowledge of the production process. But if you know what your production process is and what your end use product is, you should be able to construct a different “safe” number for your images. As Colin said, if you have a printer with a 200 line screen, you'll want 300dpi for sure. If your production device has a 150 line screen, you should be safe at 225. If you're printing to a large format printer for banners or oversized printing, you could be safe in the 100-150dpi range (depending on how close the end user will be to the final product).

I'm an in house designer at an architecture firm. Lots and lots of short-run digital work here. Plus lots of hand work (mostly in assembly). Been using InDesign since CS, adobe products since PS 2.5. I do everything from brochures to proposals to banners to presentations to books to little marketing handouts. Fave freelance project was a 600 page reunion yearbook for the naval academy.