How long should a DHCP lease be for? And Why?

I run DHCP server service on my Windows 2003 Small Business Server. In the past I've always used the default setting of 8 days for the length of time for the IP address lease.
What difference does it make if its shorter, or longer? I'm guessing that WiFi hotspots would need short leases due to the frequent turnover in computers and IP's, but what about a relatively static office network. Does it matter?

Makes sense, Talofa, but under what circumstances would somebody use a short duration lease? In other words, why is it an option? And why not make the lease never expire if longer is better?
NYCTAXIMAN: a 7 day lease means I have 7 days to get the DHCP server back up, but the files on the server, email, and DNS will be missed in 30 seconds.

Talofa,

Your DHCP lease time should be set to longer durations because if it was set to short time frames, your DHCP server would be overloaded with too many DHCP requests from hosts on the network. Hence causing network congestion just to get a IP inside your network...this is not even counting the internet or other services running on the network. Hope this explains the difference between short and long periods.

In WiFi and wired network environments, DHCP lease times are set to long durations. Why? Because even when WiFi users (for example User A) log on to grab an IP address from the WiFi router, they are only on the wireless for that period of time. When User A leaves - that IP is back in the DHCP pool to be given out. Reason for this is, when User A initially logged on wirelessly, ARP occurs. When User A is gone - the MAC is not resolved to that IP no more, because User A has physically left the wireless zone. Now User B comes along - different MAC - DHCP looks in its table and gives User B a new IP or even the same IP (in this example - we set the DHCP lease time longer, so obviously User B would get a different IP).

Static office networks don't use DHCP services because they are statically assigned. Static IP assignments are good for SOHOz (small office home office) environments and wouldn't be used in typical large networks because too much administrative overhead.

Hopefully this makes sense. Good luck!

Our DHCP scope for the lease addresses are 7 days. We also have a static environment and it doesn't hurt to have a long length of time.

One thing to keep in mind that in case your server goes down. You will have 7 days to get the server up and running.

Good Luck Mate!

In a general network environment you would want to have longer lease times.

Two reasons for short leases:
1. You would want short lease time if you have high turnover rates (Like you said public Wi-Fi) Lets say you get 50 customers per day with laptops. You have a private subnet of 255.255.255.0 you have 254 available addresses minus any company computers. You would only have enough addresses for about 5 days. So you would want much shorter lease times.

2. Office networks: If you average at the high end of the of the subnet usage (Not as big of a problem since the private subnets are more regularly used now with NAT. 10.?.?.?, 172.16.?.?, 192.168.1) . This was much more of a concern years ago when public addresses were assigned to every computer. You only got a certain amount from the ISP. This could still be a problem. If you only have one or two available address left and you have visitors like outside auditors that would want Internet access. You would want shorter leases for any computer that isn't for sick, employees on vacation, etc...

Note: You don't want it to be too low though. Because you want to keep the chatter down on the network. DHCP requests and responses do cause alot of chatter.