How long should writers wait?

When I’ve given talks, I’ve often been asked about how long writers should expect to wait to hear back on submissions and whether and when it is ok to chase. If you disagree, I’d love to hear from you but I think the answers are:

1. Agents are normally quicker to get back to you than publishers.
2. Agents usually respond to a query within a couple of weeks. If you’ve waited a month, then its in order to give a quick chase (by email rather than by telephone). In the US the system is a little different as you typically first query agents without including a sample of your writing. Here in the UK, its usual to include sample chapters with your first approach. I am certainly aiming to respond to queries within 1-2 weeks.
3. If you have been asked to send in a full manuscript to an agent, the wait is likely to be longer. I’m aiming to respond to fulls within a month, but am aware I’ve already broken my own rule!
4. Publishers may respond to you quickly, but you may equally well be waiting months. A wait of six months is not unusual, and in some cases it may be even longer. I waited ten months on my last sale of my own work. I would say that if you’ve not heard anything, it is perfectly in order for a polite chase after six months. Naturally, as an agent I am highly likely to chase publishers well before this time, but a writer without a agent unfortunately has less scope to bypass the slush pile system.