delaying autovacuum freeze via storage params?

Hello, I'd like to postpone an "autovacuum: VACUUM public.mytable (to
prevent wraparound)" and handle it manually at another time. I thought I
could set these storage parameters on the large table in question
("mytable") like this:

ALTER TABLE mytable SET (
autovacuum_freeze_min_age=10000000,
autovacuum_freeze_table_age=800000000,
autovacuum_freeze_max_age=1000000000
);

then kill the running autovacuum process, but unfortunately it just keeps
coming back:

mydb | 22734 | 05/26/2015 23:29:10 | autovacuum: VACUUM public.mytable
(to prevent wraparound)

I also tried setting the toast.autovacuum* storage parameters, as well as a
postgres reload, but neither made any difference.

Here is the table's age:

mydb=> select age(relfrozenxid) from pg_class where oid =
'mytable'::regclass;
age
-----------
203065951
(1 row)

So 203 million, which is just past the 200 million default (which is why I
started looking at this). But it's less than the 1 billion I set the
storage param to.

Here is \d+:

mydb=> \d+ mytable
Table "public.mytable"
Column | Type | Modifiers
| Storage | Stats target | Description
-------------------------+-----------------------------+-----------------------+----------+--------------+-------------
(removed al lthis)
Options: autovacuum_freeze_min_age=10000000,
autovacuum_freeze_table_age=800000000,
autovacuum_freeze_max_age=1000000000, toast.autovacuum_enabled=false,
toast.autovacuum_freeze_min_age=10000000,
toast.autovacuum_freeze_table_age=800000000,
toast.autovacuum_freeze_max_age=1000000000

I'm guessing I'm missing something here, can anyone offer suggestions or
ideas on what I should try next?

Here is my version:

mydb=> SELECT version();
version

---------------------------------------------------------------------------------------------------------------
PostgreSQL 9.3.4 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.1.2
20080704 (Red Hat 4.1.2-44), 64-bit
(1 row)

and I put my [custom settings in a gist](
https://gist.github.com/skehlet/bcdbc1ce1f212d3b7bb2)

Thanks!