How Many Connections Per IP Is Too Many

I run this a few times a day:

netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n

and get outputs like (just the bottom here, IPs removed):

8 IP #1
8 IP #2
8 . . .etc
8
9
9
9
9
9
10
10
11
12
13
14
15
18
19
25
26
32
32
91

The server runs gallery2, how many connections does an IP need just to browse the gallery? I'd like to block wget etc, but don't want to hurt search engine optimization (SEO). Is there a compromise, like limiting IPs to 5 connections, so the site still gets crawled, just slower?

DDoS deflate is installed: [url]

which permabans IPs with 150+ connections

Also what are the commands to block and unblock these IPs,