as happycat says this is just a warning message and the data should be replicating away in the background
Run the following on the distributionDB to see how much data is queued and for what tables
if exists (select * from tempdb.sys.tables where name = '##msdstatus')
drop table ##msdstatus
if exists (select * from tempdb.sys.tables where name = '##msdagents')
drop table ##msdagents
if exists (select * from tempdb.sys.tables where name = '##msdarticles')
drop table ##msdarticles
select * into ##msdstatus from msdistribution_status
select * into ##msdagents from msdistribution_agents
select * into ##msdarticles from msarticles
select ag.name, ar.article, s.undelivcmdsindistdb, s.delivcmdsindistdb
from ##msdstatus s,
where s.agent_id = ag.id and s.article_id = ar.article_id
order by undelivcmdsindistdb desc
Running this periodically will give you a good idea of how much data is being processed at given intervals and try and estimate how much time it might take.
There are lots of things to consider though.
1. Is your replicated database being hammered with more updates continually. Maybe you can pause this or ask the users to reduce the load to allow the replication to catch up?
2. What's the current database size and autogrowth growth settings of the Distribution database and its Data and Log files? If growth increments settings are quite small them maybe increase the size to minimize overhead of automatic growth.
3. As stated look at your Distribution Profile settings you can tweak values such as increasing the commitbatchsize and commitbatchthreshold but do some reading up on these options and make sure you fully understand the consequences of doing so. Upping these will make cause bigger batches of changes to replicate through as bigger transactions but if one of these transactions were to fail then a much bigger batch will get rolled back
4. Look at your subscriber activity using sp_who2 etc. Are there many reads happening on these replicated tables causing intermittent blocks to the distribution agent
As stated already get as much info as you can before deciding to make any configuration changes and make sure you fully understand what's going on in the background to cause the latency