Safety of the key and it's length

[Michał Gołębiowski]

I generated a gpg key using 'gpg --gen-key' (using GPG 1.4.6). What
concerns me is that no matter how strong agorithm would I choose, it
doesn't affect the size of the public & private key. It's probably ok,
but I wonder - how safe is the private key having exported ASCII
signature sized circa 2600 bytes? Public key is similar in size.

I see many people have keys sized 4800 bytes and even 10x bigger. How to
generate such longer keys? Is the size connected with GPG version I use?
Is my key secure? I used a passphrase sized about 40 symbols, all
English letters not making any word/phrase/etc., so it's quite long.

I would appreciate Your help.

-- 
Pozdrawiam,
Michał Gołębiowski