Do electrum wallets actually have 148 bits of security?

[jonald_fyookball]

The seed has 128 bits of entropy, so that's a 128 bit
of security against a collision.

But against a brute-force attack, the 100,000 round
hashing key-stretch gives additional security.   But,
what I just realized is that every address in the wallet
needs to run through that algorithm.  So, if an attack
wants to check, say 5 receive addresses and 5
change addresses, that's a million rounds of hashing,
or roughly 20 bits.  (and still doesn't guarantee they
will find all the addresses of a wallet). 

So you add 20 bits on top of the 128 bits, and
you're really talking about 148 bits of security
against brute force attacks against the seed.

[Abdussamad]

You only need to compute the stretched seed and master private key once. Then you can create address specific private keys at will.

[jonald_fyookball]

You only need to compute the stretched seed and master private key once. Then you can create address specific private keys at will.

i guess so, although doesn't appear to be the way electrum does it.
You still need to run ECDSA code though, which could still slow
things down to give similar result.